The board directed county staff to begin the planning, design and construction of the new center at the southeast corner of the old San Jose Medical Center site.
Board members also approved the use of $50 million for the project from the 2008 voter-approved Measure A, which allocated the money for construction of health facilities downtown.
"A modern and well-functioning clinic has been needed in the downtown core for quite a while," Supervisor Liz Kniss said in a statement. Kniss is chair of the board's Health and Hospital Committee.
Existing plans for Valley Health Center Milpitas will be adapted for use with the San Jose medical center, which is expected to open in four to five years.
In the meantime, beginning on July 1, 2011, health needs in the downtown area will be met through a temporary clinic in the Mediplex Building located at 725 E. Santa Clara St.
"We have heard loud and clear what the downtown community needs and are working hard to ensure that medical services will be available next year while the permanent clinic is being built," Supervisor George Shirakawa said in a statement.
County officials said they are approaching the site development in stages with a long-term plan that includes future expansion.
Plans for the clinic include an equal amount of space devoted to ancillary support and the public health program for women, infants and children; clinic services and urgent care; and future growth to accommodate services currently offered at the Santa Clara Valley Medical Center campus.
"Our goal is to put a clinic on site as soon as possible while developing a state-of-the-art facility to address the community's needs," county executive Jeff Smith said.