The 2006 World Series MVP passed his physical Friday and finalized a $4.5 million, one-year contract with the Blue Jays, who had planned to enter next season with John McDonald as their everyday shortstop.
General manager J.P. Ricciardi said Eckstein's attitude and offensive skills were too good to resist.
"He's great clubhouse guy. He's a leader," Ricciardi said. "The more guys we can have like this helps to lengthen our lineup."
The 5-foot-7, 175-pound Eckstein is expected bat leadoff for Toronto. The St. Louis Cardinals declined to re-sign him after he made a career-high 20 errors in 117 games this season. He was better at the plate, hitting a career-best .309 with three homers, 31 RBIs and 10 stolen bases.
Eckstein batted .364 with four RBIs and three doubles against the Detroit Tigers in the 2006 World Series as St. Louis won in five games for its first championship since 1982. He also helped the Anaheim Angels win the 2002 World Series.
"There's a lot of stability that comes with him," Ricciardi said.
Eckstein didn't need much persuading to accept Toronto's offer.
"It's definitely a great opportunity," he said. "They have a great ballclub intact. When they came and said they were interested in me, I got very excited because I think they have a good chance to win."
The move means McDonald, who signed a $3.8 million, two-year contract in September, will mostly be relegated to a backup role.
"I don't think you'll see John just sit on the bench," Ricciardi said. "It's conceivable that when we have certain guys on the mound who are groundball pitchers, Johnny may get the nod. We'll utilize him to the best of our ability to take advantage of what he is, which is a very good defensive player."
Eckstein, who turns 33 next month, was an NL All-Star in 2005 and 2006.
"He's a very good offensive player, a .350 on-base guy," Ricciardi said. "He's a tough, tough guy to strike out. You can do a lot of things with him, you can hit-and-run him. He handles the bat really well."
Eckstein, who replaced fan favorite Edgar Renteria when he joined the Cardinals before the 2005 season, has known McDonald since they played against each other in the minors. Eckstein said he'll ask McDonald to help ease his adjustment back to the American League.
The Blue Jays also agreed to a minor-league contract with catcher Sal Fasano and invited him to spring training. But Ricciardi will keep trying to strengthen his catching tandem.
"We'll still keep looking," Ricciardi said. "It just gives us a little bit of security, knowing we have someone that the pitchers like. There are a few guys still out there that could fit our needs, via free agency."