Rondon was claimed off waivers by the Giants on Wednesday, Maria I. Guardado of MLB.com reports.
Rondon was designated for assignment by St. Louis last week but will find a spot on the Giants' 40-man roster. He's been optioned to Triple-A Sacramento to begin his time with his new organization. The right-hander posted a 4.04 ERA and 1.47 WHIP in 49 innings over 18 appearances (five starts) at Triple-A Memphis to begin the year.