He was first elected to the City Council in 1976 and was re-elected twice to four-year terms, and then as mayor in 1986, winning re-election to that post in 1988, 1990 and then stepping down in 1992.
Prior to 1986, the term of mayor in Pleasanton was assigned on a rotational basis by the City Council and Mr. Mercer served in that capacity a number of times before becoming the city's first directly elected mayor.
He will be remembered for his strong support of the development of Hacienda Business Park and Stoneridge Shopping Center, to name just two of the large-scale projects he backed during his service on the council, said City Manager Nelson Fialho.
Flags at municipal buildings in Pleasanton have been lowered to half-staff in honor of the former mayor.
He is survived by a son Chuck and a daughter Shelley Despotakis.
A memorial service will be held at 1 p.m., Saturday, Jan. 25, at the Pleasanton Senior Center.