Half of a Yellow Sun received the 2007 Orange Prize for Fiction. The award is given annually for the best original full-length novel written by a woman in English; Adichie's prize amounted to £30 000. While Purple Hibiscus, her first novel, made the Orange Prize shortlist in 2004, Adichie believes that it wasn't taken as seriously as Half of a Yellow Sun, which was much more respected and reviewed.
The novel was well received by critics and included in the New York Times′s "100 Most Notable Books of the Year". In a review for The Seattle Times, Mary Brennan highlights the book as "a sweeping story that provides both a harrowing history lesson and an engagingly human narrative". The Observer's Kate Kellaway wrote: "An immense achievement, Half of a Yellow Sun has a ramshackle freedom and exuberant ambition." The New York Times had a more mixed reflection of the book, noting that "at times Adichie’s writing is too straightforward, the novel’s pace too slack" but also that "whenever she touches on her favorite themes — loyalty and betrayal — her prose thrums with life."
The Washington Post states: “Chimamanda Ngozi Adichie certainly lives up to the hype in her second novel, Half a Yellow Sun. She wowed us with this transcendent tale about war, loyalty, brutality, and love in modern Africa. While painting a searing portrait of the tragedy that took place in Biafra during the 1960s, her story finds its true heart in the intimacy of three ordinary lives buffeted by the winds of fate. Her tale is hauntingly evocative and impossible to forget.” Furthermore, Rob Nixon also captured the essence of criticism by writing a review acknowledging the historical side of the novel: “Half of a Yellow Sun takes us inside ordinary lives laid waste by the all too ordinary unraveling of nation states. When an acquaintance of Olanna’s turns up at a refugee camp, she notices that – he was thinner and lankier than she remembered and looked as though he would break in two if he sat down abruptly. – It’s a measure of Adichie’s mastery of small things – and of the mess the world is in – that we see that man arrive, in country after country, again and again and again.” Aïssatou Sidimé from San Antonio Express-News praised Adichie's writing in the book, writing that "alluring and revelatory, eloquent, prize-winning Nigerian writer Chimamanda Ngozi Adichie is quickly proving herself to be fearless in the tradition of the great African writers." Nigerian writer Chinua Achebe commented: “We do not usually associate wisdom with beginners, but here is a new writer endowed with the gift of ancient storytellers," and said about Adichie: "She is fearless, or she would not have taken on the intimidating horror of Nigeria's civil war."