Ethier was struck on the right shin during a spring training game against the Arizona Diamondbacks last Friday. Initial X-rays indicated that no bones were broken, but when soreness persisted, he had a CT scan on Tuesday that showed the tibia fracture.
The injury won't require surgery, but it's expected to keep him out until June.
The 33-year-old was slated to be the Dodgers' everyday left fielder this year. In his absence, the team is likely to turn to Carl Crawford and Scott Van Slyke.
Last season, Ethier batted .294 with 14 home runs and 53 RBIs for the Dodgers.