Interventions to promote physical activity are very limited in India. The objective of this study was to assess the effectiveness and sustainability of a peer support based physical activity (PA) intervention targeting sedentary women in Thiruvananthapuram City, India We used a non-randomized quasi-experimental study design with a comparison group. Using the Global Physical Activity Questionnaire (GPAQ) classifications, 401 sedentary women aged 18-64 years were selected by multistage cluster sampling and enrolled into the intervention (n=200) and control (n=201) arms. For the intervention arm, a culturally relevant intervention was delivered to the community stakeholders, participants and peer leaders at three subsequent intensities: intense (three months), less intense (three months) and no intervention (six months). The intervention consisted of a non-communicable disease (NCD) risk assessment, educational workshop, group counselling sessions, goal setting, handbook and peer support. The control participants received printed information on NCDs and their risk factors. PA assessments and anthropometric measurements were made at baseline, 4 , 7 and 13 months. Mixed model analysis was done to assess the difference in PA levels between groups at various time points. The proportion of women who were physically active (≥600 MET minutes per week) was significantly higher in the intervention arm compared to the control arm at 4 (58.5 % vs 10%, p= 0.001), 7 (48.5% vs 6%, p= 0.001)) and 13  month (29.6 % vs 0.6%, p =0.001), respectively. Improvements from baseline PA expended by the intervention arm compared to the control arm in MET-min / week were 990, 575, and 466 at 4 , 7 and 13 months, respectively. A PA intervention using peer support was found to be effective among women in India. Improvements in PA in the intervention arm decreased over time particularly after the no-intervention phase indicating the need for integrating it with community organizations.