San Francisco activated Jackson (elbow) from the 60-day injured list Tuesday, Evan Webeck of The San Jose Mercury News reports.
Jackson is nearly 14 months removed from Tommy John surgery and will join the Giants' bullpen for Tuesday night's game against the visiting Pirates. He allowed four earned runs over 5.1 innings on a six-appearance minor-league rehab assignment and figures to be eased in as a lower-leverage option initially.