The show is aimed at a 25- to 45-year-old audience and is broadcast across 62 stations, including Chrysalis Radio's Heart network and GMG Radio's Century and Real Radio networks.
The sponsorship was due to end on April 21 but has been extended to Baileys' marketing year end.
Helen Bagnall, Baileys brand manager, said the show has "proved a successful vehicle to encourage people to enjoy and share Baileys with friends".
'The A-List' is managed by Hit40UK, produced by UBC Media and presented by Gail Porter and Nick Snaith.
The chart focuses on artist sales rather than individual track sales and is compiled from airplay statistics, album and single sales including downloads and music DVD sales.