Familia was released by the Athletics on May 6.
Familia was designated for assignment by the Athletics on Thursday.
Familia, Trevor May and Dany Jimenez could all be used in closer situations this season, Athletics manager Mark Kotsay told Matt Kawahara of the San Francisco Chronicle on Sunday.
Familia signed with the Athletics on Saturday, Robert Murray of FanSided.com reports.
Familia was released by the Diamondbacks on Friday, Nick Piecoro of The Arizona Republic reports.
Familia allowed one run on one hit over two-thirds of an inning in Saturday's spring game against the Angels.
Familia signed a minor-league contract with the Diamondbacks on Wednesday with an invitation to spring training, according to USA Today's Bob Nightengale.
Familia elected free agency Friday after clearing waivers.
Familia (2-3) was designated for assignment after being charged with the loss Tuesday against the Yankees, Chris Cotillo of The Springfield Republican reports. The right-hander gave up three runs (two earned) on one hit with three walks and zero strikeouts.