He played in Major League Baseball (MLB) for the Pittsburgh Pirates, Brooklyn Dodgers, and Baltimore Orioles.

After returning to the Pirates, he was the starting shortstop in 1946 and 1947 before being traded to the Brooklyn Dodgers on December 8, 1947, along with Preacher Roe and Gene Mauch, for Dixie Walker, Hal Gregg and Vic Lombardi.

[1] Cox was the third baseman of a Dodgers infield in the 1950s that included Gil Hodges, Jackie Robinson and Pee Wee Reese.

Cox was acquired along with Preacher Roe by the Baltimore Orioles from the Dodgers on December 14, 1954 for a pair of minor-leaguers, infielder Harry Schwegman and right-handed pitcher John Jancse, and $60,000.

Even after a meeting with Indians' manager Al López, Cox resolved to retire and did so on June 17.` In 1058 games over 11 seasons, Cox posted a .262 batting average (974-for-3712) with 470 runs, 174 doubles, 32 triples, 66 home runs, 351 RBI, 42 stolen bases, .318 on-base percentage and .380 slugging percentage.