Rodriguez was voted in by the fans, earning his second consecutive start at third base. Sheffield and Rivera were each voted in by players, managers and coaches, earning spots on the team.
"It's very special to represent the Yankees," Rodriguez said. "To represent the American League, especially with the Yankees uniform, it's a big honor."
"I'm glad they were recognized," said manager Joe Torre.
The three players represent the lowest total for the Yankees since 1996, when they also sent three to the game in Philadelphia. That year, Wade Boggs -- like A-Rod -- was elected as the starting third baseman, while Andy Pettitte and John Wetteland were also selected.
New York had eight players at the All-Star Game last year, the most of any year during Torre's tenure as manager.
This marks the eighth time Rodriguez has been elected to start for the AL, his second as a third baseman after six at shortstop. It is his ninth overall All-Star selection. Rodriguez is hitting .319 with 20 home runs and 66 RBIs this season, making a push for the AL's triple crown.
A-Rod also ranks among the AL's league-leaders in runs scored, hits, total bases, slugging percentage, multihit games, extra-base hits and home batting average.
Rodriguez received 3,553,235 votes from fans, finishing more than 2.25 million ahead of Boston's Bill Mueller.
"It's a great honor, no question," A-Rod said. "Especially to be voted by the fans, it's overwhelming. It makes you feel pretty good."
Sheffield will also be making his ninth trip to the Midsummer Classic, his second in two years with the Yankees. Last season, Sheffield became the first player to represent five different clubs at the All-Star Game.
Sheffield is batting .297 with 13 homers and 58 RBIs in 77 games. The right fielder is among the league-leaders in walks, on-base percentage, batting average with runners in scoring position and RBIs.
"I always prepare for a vacation and don't expect to go," Sheffield said. "I just go out and play, and whatever happens, happens. It's an honor. It just means my hard work is paying off."
Sheffield finished fifth in both the fan vote and the player vote, the latter of which earned his selection to the squad.
"That's what keeps me going," Sheffield said. "As long as my peers respect what I do, like the way I play the game and go about my business, it's always good."
Rivera's All-Star selection is his second in a row, and seventh overall. Rivera has not allowed a run in any of his four All-Star appearances, earning the save in the 1997 game in Cleveland.
"I always say it's an honor to be in the All-Star Game, no matter how many times you've been there," Rivera said. "It's great to be picked to represent the American League and the Yankees."
Rivera, who is 4-2 with 18 saves and a 0.85 ERA, blew his first two save opportunities this season, but has converted his last 18 in a row, throwing 22 consecutive scoreless innings. His ERA is the best in the American League among all pitchers with at least 20 innings pitched.
"Mariano is Mariano," said Torre. "He's pretty special."
The All-Star Game, to be held at Detroit's Comerica Park on Tuesday, July 12, at 8 p.m. ET, will be televised nationally by FOX Sports and televised around the world by Major League Baseball International. ESPN Radio will provide exclusive, national radio coverage, while MLB.com will provide extensive online coverage and MLB Radio will provide exclusive play-by-play coverage of the game on the Internet.
Mark Feinsand is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.