Turnover among direct support professionals (DSPs) in community support settings for individuals with intellectual and developmental disabilities (IDD) has been regarded as a challenge since tracking of this workforce began in the 1980s. This study utilized a group randomized controlled design to test the effects of a competency-based training intervention for DSPs on site-level turnover rates over a one year period. Results suggested that, compared with the control group, sites receiving the training intervention experienced a significant decrease in annual turnover, when multiple factors were controlled. Implications, including the importance of considering quality training as a long term organizational investment and intervention to reduce turnover, are discussed.