Background: Despite holding great potential for addressing concerns regarding public health, recent systematic reviews have found effect sizes for interventions targeting physical activity to be small. Before interventions can be improved, the factors influencing outcomes must be identified. This systematic review aimed to identify predictors of success, measured in terms of engagement (eg, involvement duration) and health behavior change (eg, increased step counts), of workplace interventions targeting physical activity. Methods: A structured search of 3 databases (PubMed, PsycINFO, and Web of Science) was conducted to identify articles published between January 2000 and April 2017. For inclusion, articles needed to test a workplace intervention targeting physical activity and perform a quantitative analysis, identifying predictors of engagement or health behavior change. Results: Twenty-two studies were identified for review (median quality score = 70%). Demographic variables (eg, gender, age) were inconsistent predictors of success. However, employees in better health and physically active at baseline were found to have a greater likelihood of success. Conclusions: It appears that achieving successful results among employees at high risk of poor health outcomes remains a significant challenge for interventions. It is hoped that program developers can use this information to create effective interventions particularly for more sedentary employees.