- Soulmates: Instead as playing as individuals, the 16 Houseguests were paired off based off of compatibility forms during their audition progress. They would win and hold the title of Head of Household together, win and use the vetos together, be nominated together, and be evicted together. This twist was abandoned shortly after the third eviction, where the evicted couple found out that a re-vote would occur only between the two of them. Should a member of the pair walk or be expelled, the remaining partner would choose one member of the previously evicted couple to re-enter the game and become their soulmate.
- Previously Evicted Houseguest
- Due to Neil Garcia leaving the game, his soulmate; Joshuah Welch, had to choose either Jacob Heald or Sharon Obermueller; the previous evictees, to re-enter the game as his soulmate. Joshuah chose Sharon.
- Shortly after the fourth eviction, the Houseguests had to vote either; the Houseguest they just evicted, or the "Mystery Houseguest;" a previous evictee voted by the viewers, back into the game.
- Secret Relationship: Houseguests Ryan Quicksall and Jen Diturno were in a relationship prior to the game, and entered the house while still dating, however they weren't partnered together.
|Adam & Sheila||Allison & Ryan||Chelsia & James|
|Alex & Amanda||Matt & Natalie|
|Jacob & Sharon||Jen & Parker||Joshuah & Neil|
|Week 1||Week 2||Week 3||Week 4||Week 5||Week 6||Week 7||Week 8||Week 9||Week 10||Week 11|
|Day 1||Day 5||Day 22||Day 28||Day 35||Day 36||Day 77||Finale|
|Adam|| Ineligible|| Jen|
| Rep||Allison||James||James||Ryan||Joshuah|| Vetoed|
|Ryan|| Ineligible|| Alex|
|Sheila|| Ineligible|| Jen|
| Rep||Allison||James||Alex|| Vetoed|
|1||Sharon|| Ineligible|| Jen|
| ||James||Matt|| Rep|| Rep|| ||Adam|
|Natalie|| Ineligible|| Allison|
|Allison||James||James||Ryan||Chelsia||James|| Rep|| ||Adam|
|James|| Ineligible|| Jen|
|Allison|| Rep||Matt|| Vetoed|
| Rep|| ||Adam|
|2||Joshuah|| Ineligible|| Jen|
| ||James||James||Matt||Chelsia|| ||Ryan|
|Chelsia|| Ineligible|| Jen|
|Matt|| Ineligible|| Allison|
|Allison||James||Alex|| Rep|| ||Adam|
|Allison|| Ineligible|| Alex|
| || |
|Alex|| Ineligible|| || Mystery|
|Amanda|| Ineligible|| |
|2||Neil|| Ineligible|| |
|1||Jacob|| Ineligible|| |
|Key:||Nominated||Rep: Replacement Nominee||POV Holder||HOH||Power Couple||Vote to Re-Enter||Jury Member||Evicted||Walked|
- Note: Sharon was evicted for part of Week 1, before being chosen by Joshuah to get back into the house, replacing Neil's spot as Joshuah's soulmate.
- Note: James was evicted for part of Week 5, before being voted back into the house.
At the start of the season, the houseguests competed to declare the first Power Couple of the season. Jen and Parker were victorious, also winning ten thousand dollars, and debated on who they should send home. When Jacob caused some drama with the Power Couple, they chose to send him and his partner, Sharon out the door, making them the first evicted.
For the first Head of Household competition of the season, the houseguests competed in the "Do You Know Your Partner?" competition. Alex and Amanda were victorious and nominated pairs Ryan and Allison, along with Jen and Parker. When Neil left the game due to urgent personal matters, Joshuah was able to choose a new partner between Jacob and Sharon, which he chose the latter. Matt and Natalie won the first Power of Veto competition of the season and chose to leave the nominations the same. Jen and Parker were evicted by a 3-1 vote.
After the "Big Brother Democracy" Head of Household competition, James and Chelsia were triumphant, winning the competition. They nominated Matt and Natalie as pawns, along with Alex and Amanda, whom were their targets, to be evicted this week. Joshuah and Sharon won the Power of Veto and chose to keep nominations the same. Alex and Amanda were evicted on a 3-0 vote. It should be noted as well that Amanda and Allison had medical issues at almost the exact same time on Day 16, but both eventually returned to the house.
Following Alex and Amanda's eviction, Joshuah and Sharon won the "Words Of Love" Head of Household competition. They put up couples Matt and Natalie & Ryan and Allison for eviction, with their target being the latter. When Matt and Natalie won the Power of Veto competition "Cupid is as Cupid Does", Joshuah and Sharon nominated Adam and Sheila as the replacement nominees. Ryan and Allison were "evicted" 2-0.
Round 2 (Reset)
When the siren sounded, the houseguests were informed that the couples twist was over and that only either Ryan or Allison would go home this week. As Joshuah and Sharon still held the title of HOH, they would still only vote in case of the tie; nevertheless, it did not matter as the other houseguests voted again and Allison was evicted unanimously by a 6-0 vote.
Following his partner's eviction, Ryan won his first Head of Household competition, "Time After Time". He nominated Chelsia and Sharon for eviction, viewing them as strong. Chelsia won the "Color of Veto" Power of Veto competition and took herself off the block, which lead to the nomination of James, instead of Matt, whom many houseguests wanted to go up. James was evicted on a 5-1 vote.
Round 1 (Re-Entry)
Following James's return, he then quickly won the Head of Household competition "Big Brother Disco" and nominated Sheila and Ryan for eviction that week due to previous actions. James then won the "Trapped in the Cage" Power of Veto competition and took off nomination Sheila and replaced her with Matt, going back on a deal he made with Natalie. Matt and Ryan were tied 3-3, but James broke the tie, sending Matt to the jury house 4-3.
Following the eviction of fellow houseguest Matt, Adam won his first Head of Household competition, which was the "En Garde" competition. He nominated James and Chelsia, viewing the two as threats due to them both being good at competitions. When James won his second Power of Veto in a row, at the competition "Club Evel". Sharon was soon the replacement nominee for James and his girlfriend was soon evicted 5-0.
Following Chelsia's eviction, the houseguests competed in the "Big Brother Election" competition, leading to Natalie's first Head of Household. She nominated both James and Joshuah for eviction, seeing both as threats. Winning his third Power of Veto competition, "Big Brother Boardwalk", in a row, James pulled himself off the block. Sharon was again nominated as a replacement and her friend Joshuah was evicted from the house 3-1.
Following Joshuah's eviction, the houseguests competed in the "More.. or Less" Head of Household competition, letting Adam win his second Head of Household of the season. He quickly nominated Sharon and Sheila, stating that if the house wanted James out, they should win the Power of Veto. Ryan won "The Rainmaker" Power of Veto competition, pulling Sheila off the block. Adam put James on the block to please the house. James was evicted on a 3-0 vote.
Following James's eviction from the house, the houseguests competed in the "Glass Houses" Head of Household, leading to Sheila's first Head of Household this season. She nominated Adam and Sharon for eviction, with her intended target being Natalie. When Adam won the "PoTV" Power of Veto competition, Sheila soon nominated Natalie has the replacement. When the votes tied 1-1, Sheila broke the tie, sending her fellow ally and friend out of the house, Natalie, on a 2-1 vote.
Following fellow ally Natalie's eviction, Ryan won the Head of Household competition "Fact or Fiction". He later nominated Sheila and Sharon for eviction that week, keeping his ally Adam off the block. Ryan later won the "Big Brother Derby" Power of Veto competition and kept his nominations the same, believing Adam would evict Sheila. However, due to loyalties, Adam chose to evict Sharon from the house on a 1-0 vote.
Following the eviction of Sharon, the final three competed in the "Up The Creek" Head of Household competition, with Ryan winning. When Part 2 came along, Adam and Sheila competed in the "Who's The Guinea Pig Now?" Head of Household, with Adam winning. Ryan won the final part of the Head of Household competition, "Jury Statements" and chose to take Adam with him to the finale. Sheila was therefore evicted, 1-0.
- This season is the first season to have 16 players.
- This season is tied with Big Brother 14, Big Brother 15, Big Brother 16, Big Brother 17, Big Brother 18 and Big Brother 19 for most houseguests to start a season with 16.
- Big Brother 14 technically started with 12 houseguests and 4 coaches, however, the coaches eventually did enter the game as players themselves, therefore there were 16 houseguests at the start of Big Brother 14.
- Big Brother 17 had 17 houseguests at the end of the game due to the twin twist. Liz Nolan initially entered the house as 1 person however she switched with her sister Julia Nolan every 3-5 days. They played as 1 houseguest for the first five evictions but after that, they became two separate houseguests. Therefore 16 houseguests did enter the BB17 house, but 17 left.
- This is the only season to have two previously evicted houseguests return to the game.
- Big Brother 18 also had two evicted players return however they ended up being the same person both times. Victor Arroyo was the 3rd of 16 people evicted from BB18 however he got back in due to the Battle Back Competition twist. He reentered after beating the second evicted player, Jozea Flores (who had already beaten the first evicted player Glenn Garcia), the fourth evicted player, Bronte D'Acquisto, and the fifth evicted player, Tiffany Rousso, in head to head competition. He re-entered and was evicted again later in the season as the 10th person evicted. However the same night he was evicted he was given the opportunity to again re-enter the game, as all of the jurors were fighting to get back in. Victor beat Paulie Calafiore, Bridgette Dunning, Zakiyah Everette, and Da'Vonne Rogers in the return/HoH competition and therefore reentered the house.
- This is the first season to have a person walk from the game.
- This is the first time the houseguests played as teams.
- This is the only season to end on a Sunday.
- This is one of 3 seasons to have people seek medical attention.
- This is the only season in Big Brother history to air during the winter, due to a writer's strike.
- The spin-off series Celebrity Big Brother 1 aired during the winter of 2018, a decade later.
- Big Brother 9 is the only season from seasons 1- 12 to not have a player return to play in another season.
- This is the first season to have the same amount of jurors as pre-jurors
- This is the first season to have "couples" be paired up as duos.
|Big Brother 9 (US) Ratings - In United Kingdom|
|#||UK Air Date||Viewers||Season Avg|
|1||1||February 14, 2008||326,000|
|3||February 19, 2008||137,100||255,100|
|4||February 21, 2008||181,900||236,800|
|2||6||February 26, 2008||113,800||201,883|
|7||February 28, 2008||194,600||200,842|
|3||9||March 4, 2008||138,400||189,478|
|10||March 6, 2008||87,500||179,280|
|4||12||March 11, 2008||137,500||168,617|
|13||March 13, 2008||154,700||167,546|
|5||15||March 18, 2008||150,000||164,833|
|16||March 20, 2008||166,400||164,931|
|6||18||March 25, 2008||142,000||161,417|
|19||March 27, 2008||177,400||162,258|
|7||21||April 1, 2008||153,800||160,548|
|22||April 3, 2008||96,200||157,623|
|8||24||April 8, 2008||98,800||152,525|
|25||April 10, 2008||140,700||152,052|
|9||27||April 15, 2008||149,700||150,863|
|28||April 17, 2008||115,100||149,586|
|10||30||April 22, 2008||79,000||145,880|
|31||April 24, 2008||89,700||144,068|
|11||33||April 29, 2008||107,600||140,482|
|United States Seasons|
|English||Broadcast||1 · 2 · 3 · 4 · 5 · 6 · 7 · 8 · 9 · 10 · 11 · 12 · 13 · 14 · 15 · 16 · 17 · 18 · 19 · 20 · 21 · 22|
|Celebrity||1 · 2|