The D-Backs have used infielder Augie Ojeda and utility player Chris Burke at second base since second baseman Orlando Hudson suffered a season-ending left wrist injury Aug. 10, when an errant throw by right-hander Juan Cruz pulled Hudson's wrist into the path of Atlanta base runner Brian McCann.
"(Eckstein) is still a plus on-base guy," D-backs general manager Josh Byrnes said. "He's a tough at-bat. He's been an endearing player throughout his career. We're always trying to find ways to get better, deeper."
The acquisition came 20 days after the D-backs acquired outfielder Adam Dunn from Cincinnati.
"You can't have too many good players," D-backs manager Bob Melvin said.
Eckstein, 33, hit .277 in 76 games with Toronto, with 18 doubles, a home run and 22 RBIs. He hit .357 in his last 12 games with the Jays, who signed him to a one-year deal as a free agent last winter.
A career .285 hitter, Eckstein played on World Series winners at Anaheim in 2002 and St. Louis in 2006, when he was the Series MVP, hitting .364 with four RBIs. He was an NL All-Star with the Cardinals in 2005 and 2006.
Eckstein was to report to the D-Backs on Monday, when they begin a three-game series against the Cardinals at Chase Field.
DODGERS 8, DIAMONDBACKS 1: The D-backs' lead in the NL West was cut to 2-1/2 games when the Dodgers beat RHP Brandon Webb on Sunday to win the final game of a weekend series, denying Webb the chance to become the majors' first 20-game winner. Webb gave up eight runs, six earned, tying a career-high for runs allowed. He also tied his career high with five walks while failing to become only the sixth pitcher since 1990 to win 20 games before Sept. 1. 3B Mark Reynolds' 26th homer -- a solo shot -- was the D-backs' only run.