Objective To examine the overall effectiveness of interventions for reducing adult sedentary behaviour and to directly compare environmental, behavioural and multicomponent interventions.

Design Intervention systematic review with meta-analysis.

Data sources Ovid PsycINFO, Ovid MEDLINE, EBSCOHost CINAHL, EBSCOHost SPORTDiscus and PubMed were searched from inception to 26 July 2017.

Eligibility criteria Trials including randomised controlled trials, quasi-randomised, cluster-randomised, parallel group, prepost, factorial and crossover trials where the primary aim was to change the sedentary behaviour of healthy adults assessed by self-report (eg, questionnaires, logs) or objective measures (eg, accelerometry).

Results Thirty-eight trials of 5983 participants published between 2003 and 2017 were included in the qualitative synthesis; 35 studies were included in the quantitative analysis (meta-analysis). The pooled effect was a significant reduction in daily sitting time of −30.37 min/day (95% CI −40.86 to −19.89) favouring the intervention group. Reductions in sitting time were similar between workplace (−29.96 min/day; 95% CI −44.05 to –15.87) and other settings (−30.47 min/day; 95% CI −44.68 to –16.26), which included community, domestic and recreational environments. Environmental interventions had the largest reduction in daily sitting time (−40.59 min/day; 95% CI −61.65 to –19.53), followed by multicomponent (−35.53 min/day; 95% CI −57.27 to –13.79) and behavioural (−23.87 min/day; 95% CI −37.24 to –10.49) interventions.

Conclusion Interventions targeting adult sedentary behaviour reduced daily sitting time by an average of 30 min/day, which was likely clinically meaningful.