Sedentary behaviour - i.e., low energy-expending waking behaviour while seated or lying down - is a health risk factor, even when controlling for physical activity. This review sought to describe the behaviour change strategies used within interventions that have sought to reduce sedentary behaviour in adults. Studies were identified through existing literature reviews, a systematic database search, and hand-searches of eligible papers. Interventions were categorized as 'very promising', 'quite promising', or 'non-promising' according to observed behaviour changes. Intervention functions and behaviour change techniques were compared across promising and non-promising interventions. Twenty-six eligible studies reported 38 interventions, of which 20 (53%) were worksite-based. Fifteen interventions (39%) were very promising, 8 quite promising (21%), and 15 non-promising (39%). Very or quite promising interventions tended to have targeted sedentary behaviour instead of physical activity. Interventions based on environmental restructuring, persuasion, or education, were most promising. Self-monitoring, problem solving, and restructuring the social or physical environment were particularly promising behaviour change techniques. Future sedentary reduction interventions might most fruitfully incorporate environmental modification and self-regulatory skills training. The evidence base is however weakened by low-quality evaluation methods; more RCTs, employing no-treatment control groups, and collecting objective data, are needed. Supplemental_PRISMA_checklist.pdf Supplemental References.pdf Supplemental Table_1.pdf Supplemental Table_2.pdf Supplemental Table_3.pdf Supplemental Table_4.pdf Supplemental Table_5.pdf.