Born in Fairfield, Alabama, and raised in Pittsburg, California, Malmberg batted and threw right-handed, stood 6 ft 1 in (1.85 m) (185 cm) tall and weighed 170 pounds (77 kg) during his active career.

Originally a member of the Cleveland Indians farm system, he reached Triple-A with the San Diego Padres of the Pacific Coast League in 1951, and spent the 11 of the next 12 years at the top level of the minors, toiling also for the Indianapolis Indians, Charleston Senators and Minneapolis Millers of the American Association, and the PCL's San Francisco Seals and Seattle Rainiers.

After Pesky's firing at the end of 1964, Malmberg embarked on an 11-year minor league managerial career in the Baltimore Orioles, Kansas City Royals and Oakland Athletics organizations.

When the Seattle Mariners were formed as an American League expansion team set to begin play in 1977, Malmberg was appointed the club's first third-base coach on the staff of manager Darrell Johnson.

But Malmberg was suffering from terminal pancreatic cancer and he died in San Francisco at age 51, five months before the Mariners played their first official game.