Introduction: Insufficient physical activity (PA) and excess weight increase illness risk for women. Face-to-face interventions can help increase PA; yet they are often inaccessible. With growing interest in web-based interventions, we delivered an email-based intervention to increase PA in women who were overweight/obese and investigated participants' acceptability of the intervention. Methods: The intervention consisted of 6 weekly emails, the provision of a Polar A300 activity monitor (with smartphone/web apps), and a copy of PA guidelines. Emails were developed using self-determination theory (SDT) and designed to enhance autonomous motivation by fostering psychological needs of competence, autonomy, and relatedness. Well-established motivational and behaviour change techniques were used to promote needs satisfaction. Fourteen women (Mean-age=33.4 years, Mean-BMI=31.2kg/m2) completed an acceptability survey post-intervention. Results: Qualitative data indicate most participants were satisfied with the intervention and appreciated that emails prompted self-reflection, kept them on track and accountable, provided informational support, and were non-pressuring. Further, participants found the monitor "enjoyable" and "helpful." This was corroborated by the quantitative data as 71.4% said the monitor was "very valuable/absolutely valuable," 71.7% would "very probably/definitely" still use one, and 85.7% wore it >5 days/week for >8 hours/day and checked it "occasionally/frequently/very frequently." Potential threats to acceptability include: "long," "text-heavy" emails, lack of personal contact, and large, non-aesthetic monitors. Conclusions: Results suggest this email-delivered SDT-based intervention may be an acceptable low-contact tool to promote PA in this population, although improvements are warranted, as are studies ascertaining its efficacy. Nonetheless, results may inform the development of similar interventions in other contexts.