The award winning writer won the “Best of the Best” award as part of the celebrations to mark 20 years of the annual £30,000 prize.
Adicihie said she was “grateful and happy”, adding: “This is a prize I have a lot of respect and admiration for.”
The 38-year-old novelist continued saying,: “Over the years it’s [the Baileys Women’s Prize for Fiction] brought wonderful literature to a wide readership that might not have found many of the books.
“I have a lot of respect for the books that have won in the past 10 years and also for the books that have been shortlisted – I feel I am in very good company.”
Other winners of the Baileys Prize from the last decade include Zadie Smith for On Beauty, Rose Tremain for The Road Home and Eimear McBride for A Girl is a Half-formed Thing.
The winner of Best of the Best of the prize’s first decade in 2005 was Andrea Levy’s Small Island, which won the main title in 2004.
Established in 1996, the Baileys Women’s Prize for Fiction – first known as the Orange Prize for Fiction, is awarded to the best novel of the year written by a woman, with Baileys taking over sponsorship in 2014.
Adichie’s novel was chosen by the chairs of the judging panels from the last 10 years.
They included the novelist Joanna Trollope, actresses Miranda Richardson and Sheila Hancock and broadcasters Fi Glover, Kirsty Lang and Muriel Gray.
Gray, who chaired the judges the year Adichie won the Baileys Prize, had this to say about her novel: “While it’s sometimes pompous to call a book ‘important’, it’s appropriate to say it of Half of a Yellow Sun.
“For an author, so young at the time of writing, to have been able to tell a tale of such enormous scale in terms of human suffering and the consequences of hatred and division, whilst also gripping the reader with wholly convincing characters and spell-binding plot, is an astonishing feat.”