ABSTRACTDelivery of interventions through group sessions allows for in-depth discussions and creates opportunities for group members to work together to identify and solve common problems. However, low attendance may limit impact. We explored factors affecting attendance, active participation, and behavior change in an integrated group-based child development and maternal and child health intervention in Bangladesh. Community health workers (CHWs) facilitated two sessions a month including material on child stimulation; water, sanitation, and hygiene; nutrition, maternal depression, and lead exposure prevention. Sessions were conducted with 320 pregnant women and mothers with children younger than 24 months, in 16 villages in Kishoreganj district. After 4 and 9 months of intervention, we conducted focus group discussions and in-depth interviews with mothers (n = 55 and n = 48) to identify determinants of attendance and behavior change, and to examine potential for intervention scale-up. Recruiting family members to assist with childcare resulted in improved attention during sessions. Adopting a storytelling format for presentation of session materials resulted in more engaged participation during courtyard sessions. Session attendance and behavior change, especially purchasing decisions, were difficult for participants without the support of male heads of the household. Selecting a rotating leader from among the group members to remind group members to attend sessions and support CHWs in organizing the sessions was not successful. Facilitating self-appraisals and planning for water and sanitation allowed participants to identify areas for improvement and track their progress. Key determinants of a participant’s attendance were identified, and the resulting intervention shows promise for future implementation at scale.