"If you really want a winning ticket, this is it," the California senior senator said on ABC's "This Week with George Stephanopoulos."
"I've looked at every other possible candidate," said Feinstein. "No one brings to a ticket what Hillary brings -- 18 million people committed to where she's going."
Feinstein said she is convinced Clinton would help Obama's chances of defeating presumptive Republican nominee John McCain by bringing her strong support among women.
Feinstein also said the meeting between Obama and Clinton last week helped begin the process of mending fences between the two Democratic rivals for the nation's highest office.
"The nerve endings have to be healed. They are being healed," Feinstein said, adding that Clinton "wanted to have that meeting ... She wanted one opportunity to sit down with Sen. Obama, just the two of them, and, I think, establish a sense of rapport between them, I think put aside what had happened on the campaign trail, and I think be able to see if -- I used the word nerve endings for such -- that they could forge some kind of a positive bond and working relationship."