List of episodes

Season 2: 2010-2011
Season two contains 26 half episodes and originally aired from October 2010 to mid-2011. Their titles and production codes were revealed on the Frederator Blog.

Season 3: 2011-2012
Season 3 contains 26 half episodes and originally aired on July 2011 to February 2012. Their titles and production codes were revealed on April 6, 2011 on the Frederator Blog. . Season 3 saw the debut of many recurring characters, such as Fionna and Cake, the Earl of Lemongrab, Flame Princess, Mr. Pig, and Abracadaniel.

Season 4: 2012
Season 4 premiered on April 2, 2012. Episode titles were posted on the Frederator Blog in March 2012.

Writing of the season had started by May 2011. According to Andy Ristaino, by February 2012, the season had been written, storyboarded and approved. The season saw the premiere of the 100th episode of the series, "The Hard Easy" (previously titled "Prince Huge"). Adam Muto reported that characters not seen since the earlier seasons would return, with The Earl of Lemongrab, Magic Man, the Lich, Hunson Abadeer and Neptr being confirmed to return. Prior to the season's airing, Adam Muto said that Marceline's backstory would be explored further, and Jeremy Shada also mentioned that Marceline and Ice King would sing together. Both took place in the episode "I Remember You." The season featured guest voices by Donald Faison, George Takei, Erik Estrada, Andy Milonakis, Emo Phillips, Bobcat Goldthwait and Susie Essman. The season featured one complete two-parter ("Return to the Nightosphere" and "Daddy's Little Monster"), however the season's introductory episode was a continuation of the season 3 finale, and the season 4 finale continued into season 5's two-part opening episode.

Season 5: 2012-2014
In an interview with Charlie Jane Anders, Pendleton Ward revealed that the writers were working on season 5. Jesse Moynihan revealed that as of July 30, 2012, works on season 5 storyboards has already ended; however, he may have only been referring to the first 26 episodes. He also stated that the pairs working on those were: Jesse Moynihan and Ako Castuera, Cole Sanchez and Rebecca Sugar, Tom Herpich and Steve Wolfhard, Skyler Page and Somvilay Xayaphone with the help of Kent Osborne. Season 5 began with the airing of a two-parter on Monday November 12, 7:30 p.m. (ET/PT), 2012, on Cartoon Network titled "Finn the Human"/"Jake the Dog." The episode titles and production codes were revealed by the Frederator blog. It was also revealed that this season was to contain a one-hour special (with the production codes 1014-125, 1014-126, 1014-127, and 1014-128), but it was pushed off for later, and eventually cancelled. As of June 30, 2013, storyboarder Jesse Moynihan revealed that the one-hour "movie" was intended to divide season 5 in half, which has now been extended by another 26 episodes. On November 26, 2013, Jesse Moynihan announced on Twitter that the special had been scrapped. This season consists of twice as many episodes as a normal season, making it the longest season so far. According to iTunes' synopsis, season 5.2 "heats up, cools down, then heats back up again as Flame Princess battles Ice King in a mathematical battle of the elements! And what will Princess Bubblegum discover in the aftermath?! Then P-Bubs joins Marceline on a top-secret mission in search of…wait…that’s top secret! Nice try!! Then take a trip with Finn and Jake to the birthplace of BMO. It will be so cool. But also hot."

Season 6: 2014-2015
On January 28, 2013, it was officially announced that the show had been renewed for a sixth season. On June 30, 2013, storyboarder Jesse Moynihan announced that he would start season six the following week. Season six is not to be confused with the second half of season five; the latter of the two has been referred to as season 5.2 by the writing staff. The sixth season premiered on April 21, 2014, with the airing of the episodes "Wake Up" and "Escape from the Citadel."

Following season 5's cliffhanger finale, the reveal of Finn's dad was prominently teased in the promos leading up to the season premiere. It was also confirmed by the writing staff that a total of eight episodes in season 6 will involve Finn and his dad, featuring some of the show's most cohesive storytelling to date. Adam Muto has also confirmed that season 6 will feature more episodes than a standard season, but fewer episodes than the entirety of season 5.

Season 7: 2015-2016
On July 25, 2014, the series was renewed for a seventh season. According to Tom Herpich and Steve Wolfhard, the staff started to pitch story lines in late September of 2014. According to storyboard artist Jesse Moynihan, production for the season began in October of 2014. Adam Muto later revealed on Spring.me that the season will contain around the same number of episodes as the sixth season, although he did not provide an exact number. There will also be a stop motion episode in this season. On October 9, 2015 It was announced for release date from season 7 will be aired on November 2, 2015.

Season 8: 2017
On July 7, 2015 Adventure Time was renewed for an eighth season according to The Hollywood Reporter. Storyline writing for season eight began on August 10, 2015. On September 8, 2015, storyboarding began according to Sam Alden. January 23, 2017 marks the premiere of season 8, featuring two back-to-back episodes "Two Swords" and "Do No Harm."

Season 9: 2017-2018
Adventure Time was confirmed for a ninth season by Kent Osborne on July 21, 2016. It’s the final season of the show.

Special
On November 17, 2017, it was announced that a bonus episode entitled "Diamonds and Lemons" would be produced by 's gaming studio  and air sometime in the summer of 2018. The episode will be based on the sandbox video game .[29] [30]  According to Adam Muto, "Diamonds and Lemons" was produced separately from the show's final season.[285]

Unproduced episodes
These episodes were planned, and are known from design documents released by Frederator Studios in 2009 during the production of the first season. However, they were not produced for season one, and it is unlikely that they will actually be made into full episodes but it isn't unheard of for an unproduced episode to get produced eventually. Adam Muto has confirmed "Jakesuit" eventually worked its way into "The Silent King," and it got its own full episode only five seasons later, "Jakesuit" became "Jake Suit." "Brothers in Insomnia" was originally episode #692-002. However, it was scrapped, and its production number was taken by "Rainy Day Daydream," which was actually one of the last episodes produced for season one.

The Frederator blog also posted notes for an episode that was thought to be titled "You're a Beautiful Dancer." However, Adam Muto later confirmed that "You're a Beautiful Dancer" was just a quote that Finn was saying to Jake and was never meant to be an episode title. He stated that the page in question only contained random story ideas that were never fully developed into episodes.