The 6-foot-7, 260-pound Pineda was named as a replacement for Detroit's Justin Verlander, who started for the Tigers on Sunday and thus won't be eligible to play Tuesday.
Seattle's Felix Hernandez was in the same boat as Verlander, needing to be replaced after he threw Sunday against the Angels. Toronto's Ricky Romero will take Hernandez's spot, though Hernandez will go to the game and be part of the festivities.
Pineda, 22, is 8-6 with a 3.03 ERA and has been one of the American League's top new stories this year. The hard-throwing youngster has 113 strikeouts and just 36 walks in 113 innings, with opposing batters hitting .198 against him.
Asked last week what it would mean if he were named to the All-Star team, the Dominican native's eyes grew wide.
"Oh wow," Pineda said. "I don't know. I might just die. Maybe Pineda dies."
That reaction didn't lessen any as he got the official word just prior to the Mariners' 4-2 loss to the Angels on Sunday.
"Today is a big day," he said. "I'm very excited."
He will join Mariners closer Brandon League and Hernandez at the All-Star festivities, and manager Eric Wedge said it would be a valuable time for the youngster.
"It's a great experience for him, to be in that setting surrounded by great baseball players," said Wedge. "It'll be another set of firsts for him."
Pineda's family is in the Dominican, so Mariners bullpen coach Jaime Navarro -- who has mentored Pineda for several years and is living with him this season in Seattle -- will accompany the youngster to Phoenix.
The Mariners are trying to monitor Pineda's workload, as he's on pace to throw 203 innings at this point. As a result, they'll push back his next start to Tuesday, July 19, giving him nine days between his last outing Saturday in Anaheim and his next appearance in Toronto.
But Wedge said he isn't worried about whether the youngster pitches in the All-Star Game.
"It'd be great if he gets in the game," Wedge said. "That would be great for him."