The Rays announced the news on Twitter on Friday.
MLB confirmed he'll replace Cleveland Indians starter Corey Kluber.
Snell, who led the AL in ERA when the rosters were announced Sunday, was almost universally viewed as the biggest snub from the Midsummer Classic—until now.
Although he was always expected to end up on the AL squad either as an injury placement or taking the place of a starter who pitches Sunday, making them unavailable for the All-Star Game, he said that wouldn't bring the same sense of satisfaction.
"I feel like being an alternate, it's not satisfying," he told reporters. "I feel like I earned it but being an alternate, it doesn't feel the same."
Snell now ranks third in the Junior Circuit in ERA (2.27) after a poor outing Thursday against the Minnesota Twins. His other numbers are equally strong with a 12-5 record, 1.07 WHIP and 134 strikeouts in 119 innings across 20 starts.
It's the 25-year-old Washington native's first All-Star Game selection.