The Malian midfielder has signed with los Che until the end of the season, and has the option of a further year, subject to the completion of his medical.
The veteran Malian midfielder had enjoyed a successful Liga career, first turning out for Sevilla in the 2007-08 season before moving to Camp Nou.
He left Spain after four years in Catalunya for Chinese side Dalian Aerbin in 2012, but has now returned to the Primera Division, initially for the next five months.
"The central midfielder Seydou Keita, subject to medical checks, has signed with Valencia until June 30, with the option of a further year," a club statement read.
The 34-year-old began his professional career in France, turning out for Marseille, Lorient and Lens before his first move to Spain.