Background: Gastrocnemius injuries are a common lower extremity injury in elite baseball players. There are no current epidemiological studies focused on gastrocnemius injuries in professional baseball players that provide information on the timing, distribution, and characteristics of such injuries. Hypothesis: Gastrocnemius injury in professional baseball players is a common injury that is influenced by factors such as age, player position, and time of season. Study Design: Descriptive epidemiological study. Methods: Based on Major League Baseball’s (MLB’s) Health and Injury Tracking System (HITS) database, gastrocnemius injuries that caused time out of play for MLB and Minor League Baseball (MiLB) players during the 2011-2016 seasons were identified. Player characteristics, including age, level of play, and position at time of injury, were collected. Injury-specific factors analyzed included date of injury, time of season, days missed, and activity leading to injury. Results: A total of 402 gastrocnemius injuries (n = 145, MLB; n = 257, MiLB) occurred during the 2011-2016 seasons. MLB players were significantly older at the time of injury (30.1 years, MLB; 23.9 years, MiLB; P < .001). Base running (36.1%) was the most common activity causing the injury, followed by fielding (23.6%), with 50.3% of base-running injuries sustained on the way to first base. In MLB players, gastrocnemius injuries were most common in infielders (48.3%), followed by pitchers (27.6%) and then outfielders (17.9%), while for MiLB players the injuries were more evenly distributed (33.5%, 28.8%, and 30.7%, respectively). The frequency of injuries in MLB players dropped off after the start of the regular season, whereas MiLB players had a consistent injury rate throughout the year. Conclusion: Gastrocnemius injuries are a common cause of lower extremity injury in professional baseball players, resulting in significant time out of play. Base running, particularly to first base, was the most common activity during injury. Outfielders had the fewest injuries; however, they required the longest time to recover. This study provides the first investigation to date with the HITS database to examine the characteristics and distribution of gastrocnemius injuries in professional baseball players, offering insight into risk factors, injury prevention, and recovery expectations.