Ripken was born in Havre de Grace, Maryland, the son of Violet "Vi" Ripken (nee Roberta) and Cal Ripken Sr. He has German, English, and Irish ancestry. Though the Ripkens called Aberdeen, Maryland, their home, they were often on the move because of Cal Sr.'s coaching duties with the Baltimore Orioles organization. Cal Sr., in fact, was in Topeka, Kansas with one of his teams when his son was born.

Ripken was drafted by the Baltimore Orioles in the second round of the 1978 Major League Baseball draft 48th overall. Despite a story written by SABR, Ripken was selected with the Orioles' predetermined draft pick, not through a forfeited pick from the Boston Red Sox after the Sox selected Dick Drago in the 1977 re-entry draft. The Orioles would select catcher Cecil Whitehead with the pick they received from Boston two picks after Ripken. On deciding to go straight from high school to the professional level, he said, "When the colleges started coming around, Dad and I talked about mostly whether I was going to pursue a career in baseball. If I had the ability, the feeling was to get on with it, and if it didn't work out, start over again in college at 25 or 26." Ripken played both pitcher and shortstop in high school; in fact, the Orioles were the only team not just interested in his pitching ability. The Orioles decided to start him playing shortstop in the minor leagues, deciding it would be easier for him to transition back to pitching if necessary than it would be for him to start hitting again.  To begin Ripken's minor league career, the Orioles assigned him to the Bluefield Orioles of the rookie Appalachian League. He batted .264 with 63 hits, 0 home run, and 24 RBIs, failing to make the league's all-rookie team. In 1979, Ripken moved up to the Single-A Miami Orioles of the Florida State League. Shortly into the season, Miami manager Lance Nichols decided to move Ripken to third base, saying, "Cal was having some problems at short, so naturally I decided to shift him to third ... Third base was a perfect fit for Cal and our team." On July 2, Ripken hit his first professional home run, a game-winner in the 12th inning against Gary Abone of the West Palm Beach Expos. Ripken batted .303, hit five home runs, led the league with 28 doubles, and had 54 RBIs while playing in all 105 of Miami's games. He was named an All-Star after the season. His performance earned him a brief call-up to the Charlotte Orioles of the Double-A Southern League; Ripken batted .180 in a month with them, albeit with three home runs.  Ripken began 1980 with Charlotte. His manager at Charlotte, Jimmy Williams, predicted him to set the team home run record, and Ripken did not disappoint. At season's end, he had 25 home runs, besting the previous record by four. He also had 28 doubles, 78 RBIs, and a .492 slugging percentage. Ripken was named an All-Star while helping Charlotte win the Southern League championship.  In 1981, Ripken was added to Baltimore's 40-man roster. He attended spring training with the Orioles, but was sent to the Rochester Red Wings of the Triple-A International League to start the season. At Rochester, Ripken played in the longest professional baseball game. Ripken started at third base and played all 33 innings against the Pawtucket Red Sox (which featured another future Hall of Famer, Wade Boggs) in a game that took parts of three days to complete. Ripken hit 23 home runs for Rochester while batting .288 with 75 RBIs in 114 games. He was named the International League Rookie of the Year.

How did his team perform?
He batted .264 with 63 hits, 0 home run, and 24 RBIs, failing to make the league's all-rookie team.