OBJECTIVE - Behavioral interventions targeting "free-living" physical activity (PA) and exercise that produce long-term glycemic control in adults with type 2 diabetes are warranted. However, little is known about how clinical teams should support adults with type 2 diabetes to achieve and sustain a physically active lifestyle. RESEARCH DESIGN AND METHODS - We conducted a systematic review of randomized controlled trials (RCTs) (published up to January 2012) to establish the effect of behavioral interventions (compared with usual care) on free-living PA/exercise, HbA1c, and BMI in adults with type 2 diabetes. Study characteristics, methodological quality, practical strategies for increasing PA/exercise (taxonomy of behavior change techniques), and treatment fidelity strategies were captured using a data extraction form. RESULTS - Seventeen RCTs fulfilled the review criteria. Behavioural interventions showed statistically significant increases in objective (standardized mean difference [SMD] 0.45, 95% CI 0.21-0.68) and self-reported PA/exercise (SMD 0.79, 95% CI 0.59-0.98) including clinically significant improvements in HbA1c (weighted mean difference [WMD] -0.32%, 95% CI -0.44% to -0.21%) and BMI (WMD -1.05 kg/m2, 95% CI -1.31 to -0.80). Few studies provided details of treatment fidelity strategies to monitor/improve provider training. Intervention features (e.g., specific behavior change techniques, interventions underpinned by behavior change theories/ models, and use of ≥10 behaviour change techniques) moderated effectiveness of behavioral interventions. CONCLUSIONS - Behavioral interventions increased free-living PA/exercise and produced clinically significant improvements in long-term glucose control. Future studies should consider use of theory and multiple behavior change techniques associated with clinically significant improvements in HbA1c, including structured training for care providers on the delivery of behavioural interventions.