Purpose To assess the impact of workplace-based return-to-work (RTW) Coordinators' interpersonal and functional activities on RTW outcomes. Methods Multivariable logistic regression analyses of cross-sectional and longitudinal survey responses of 632 injured workers with at least 10 days of work absence in Victoria, Australia, adjusting for demographic and other workplace factors. Outcome was being back at work for at least 1 month, measured at both baseline and 6 month follow-up survey. Participant responses to stressfulness of Coordinator interactions were dichotomised into good and poor and evaluated as a proxy for Coordinators' interpersonal activities, while having a RTW plan was evaluated as a proxy for functional activities. Results At baseline, RTW plans doubled the odds of RTW (OR 2.02; 95% CI 1.40-2.90) and attenuated the impact of good Coordinator interactions (1.14; 0.77-1.70). At 6-month follow-up, the opposite was observed: good interactions nearly doubled odds of RTW (1.90; 1.22-2.95) while RTW plans were non-significant (1.02; 0.68-1.54). Conclusions Differences between when the two Coordinator activities were effective may be due to the nature of claimants who RTW in each survey period. Length of shorter-duration claims are influenced by injury related factors, while psychosocial factors tend to be more important for longer-duration claims. Such factors may determine whether a claimant is more likely to respond to Coordinators' functional or interpersonal activities. The findings have important implications for increasing Coordinator effectiveness.