The publication's bosses are demanding over $1.6 million (Gbp1 million) from the former Tour De France champion, who was stripped of all his cycling titles and banned from the sport for life earlier this year (12), amid an investigation into his alleged illegal drug use.
Armstrong successfully sued the publishers after newspaper editors reprinted doping claims against him from a book in 2005, and won a $485,000 (Gbp303,000) settlement.
Following claims from officials at the U.S. Anti-Doping Agency this year that suggested Armstrong took performance enhancing drugs, Sunday Times bosses have moved to win back their cash.
In a letter to Armstrong's lawyers, obtained by the Associated Press, the publishers write, "It is clear that the proceedings were baseless and fraudulent. Your representations that you had never taken performance enhancing drugs were deliberately false.
"The Sunday Times is now demanding a return of the settlement payment plus interest, as well as its costs in defending the case."