The first season follows Carrie Mathison, a Central Intelligence Agency operations officer who, after conducting an unauthorized operation in Iraq, is put on probation and reassigned to the CIA's Counterterrorism Center in Langley, Virginia. In Iraq, Carrie was warned by an asset that an American prisoner of war had been turned by al-Qaeda. Carrie has also been diagnosed with bipolar disorder, a fact that she conceals from the CIA. She surreptitiously receives medication for the disorder from her sister.

Carrie's job grows complicated when her boss, Director of the Counterterrorism Center David Estes, calls Carrie and her colleagues in for an emergency briefing. Carrie learns that Nicholas Brody, a U.S. Marine Sergeant who had been reported as missing in action since 2003, has been rescued during a Delta Force raid on a compound belonging to terrorist Abu Nazir. Carrie comes to believe that Brody is the American prisoner of war whom her asset in Iraq was talking about. However, the federal government and her superiors at the CIA consider Brody a war hero. Later, another Marine captured at the same time, Tom Walker, is also found to be still alive, casting doubt on which of the Marines is the suspected spy.

Realizing it would be nearly impossible to convince her boss to place Brody under surveillance, Carrie approaches the only other person she can trust, her mentor, Saul Berenson. The two must now work together to investigate Brody and prevent another terrorist attack on American soil. Eventually, Brody plans to assassinate the Vice President with a suicide vest but falters at the last moment after an emotional conversation with his daughter Dana. Carrie becomes more paranoid that Brody plans to carry out a terroristic act.

On Rotten Tomatoes, the season has an approval rating of 100% with an average score of 9.3 out of 10 based on 32 reviews. The website's critical consensus reads, "Homeland is an addictive, politically resonant spy thriller and compelling character study that benefits from superb performances." The first season scored a Metacritic rating of 92 out of 100 from 28 critics. TV Guide named it the best TV show of 2011 and highly applauded the performances by Damian Lewis and Claire Danes. Metacritic determined Homeland to be the second-best TV show of 2011 according to major TV critics, by aggregating the critics' year-end top-ten lists.

Hank Stuever of The Washington Post gave the pilot episode an A−, saying "What makes Homeland rise above other post-9/11 dramas is Danes's stellar performance as Carrie — easily this season's strongest female character," and that "The latter half of the first episode is exhilarating. I'm hooked." Matthew Gilbert of The Boston Globe said it was his favorite drama pilot of the season, giving it an A. Entertainment Weekly's Ken Tucker gave it an A−, stating "It's the fall season's most intriguing, tense puzzler." IGN TV gave it a positive review, saying that it was an "ace thriller" that also managed to have something to say about the "War on Terror". The seventh episode, "The Weekend", was described by both the creators of the show and Damian Lewis as a "watershed" episode.

Former US President Barack Obama has praised the show.

Homeland: The Complete First Season was released as a widescreen region 1 four-disc DVD and three-disc Blu-ray box set in the United States and Canada on August 28, 2012. In addition to all 12 episodes that had aired, it includes audio commentary on the pilot episode, deleted scenes, "Homeland Season One: Under Surveillance" featurette, and "Week Ten: A Prologue to Season 2" featurette. The same set was also released on September 10, 2012, in region 2.

The season is also available for streaming online via Hulu, as of August 1, 2016.