LaRue was signed as the backup catcher to Yadier Molina.
The Cardinals also signed two right-handed pitchers to Minor League contracts: Dewon Brazelton and John Wasdin.
LaRue, 33, is regarded as a top-notch defensive receiver but struggled with the bat this year, his only season with Kansas City. He batted just .148 (25-for-169) in 66 games with four home runs and 13 RBIs.
But he showed an outstanding arm, throwing out 14 of 40 would-be basestealers, 35 percent. He's tied with Detroit's Ivan Rodriguez for second in best efficiency, 37 percent, since 2001, trailing only Washington's Brian Schneider's 38 percent.
The Royals had a 24-31 record in the 55 games he started behind the plate, and he caught five of the Royals' six shutouts in 2007.
The Royals obtained LaRue in a trade from Cincinnati, where he played for eight seasons. He was the Reds' primary catcher for five years and had 10 or more homers and 50-plus RBIs in each season. However, in 2006, LaRue was limited to 72 games after undergoing right knee surgery during Spring Training.
During his Reds' career, LaRue had a .239 average and 84 home runs, with a high of 16 in 2003.
A right-handed batter, he replaces veteran catcher Gary Bennett, who became a free agent after two years with the Cardinals.
Brazelton, 26, was in camp with the Royals last spring and pitched for Triple-A Omaha and was 0-4 with a 7.11 ERA in four games before being released. Moving to the Pittsburgh organization, he was 5-5 with a 3.53 ERA in 15 starts for Double-A Altoona.
His last Major League turn came in 2006, when he was 0-2 with a 12.00 ERA in nine games for San Diego.
Wasdin, 35, has a 39-39 record and a 5.28 ERA in a 12-year Major League career. Last year, he broke camp with the Pirates and was 1-1 in 12 relief appearances but then had a right thumb sprain. His season ended in late July because of a wrist injury.
Wasdin has also pitched for Oakland, Boston, Colorado, Baltimore, Toronto and Texas. In 1999 for the Red Sox, Wasdin began the season with a 7-0 record as a reliever and finished 8-3, matching his career high for wins reached as an A's starter in 1996.
Wasdin was the A's first-round Draft choice in 1993.
He and Brazelton will be invited to Spring Training as non-roster players.
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.