Background: Some evidence suggests that physical activity programs mainly attract employees who are already active. This study examined the degree to which baseline physical activity was associated with enrollment in worksite walking clubs. Methods: All variables were measured at baseline. Walking club participation was measured over 2 years. There were 642 individuals from 3 worksites with complete data available for logistic regression analyses. Results: Baseline physical activity [OR (95% CI) = 1.00 (0.99, 1.01)] was not a significant predictor of walking club participation. Participants who were older [OR = 1.03 (1.01, 1.04)] or indicated more social support for physical activity [OR = 1.13 (1.02, 1.25)] had significantly higher odds of participation relative to those who were younger or indicated less social support, respectively. In addition, men [OR = -0.25 (0.18, 0.36)] and employees from the second worksite [OR = -0.41 (0.25, 0.67)] had significantly lower odds of participation relative to women and employees from the first or third worksites, respectively. Sensitivity analyses arrived at similar conclusions. Conclusions: Worksite walking clubs were appealing across varying levels of physical activity. Future research should improve marketing and program design to engage harder-to- reach segments of the workforce, particularly young men and those with limited social support.