Mothers undergo extensive changes after birth and are a priority group at risk of mental health issues and physical inactivity. Team sport participation often provides additional social and mental benefits beyond physical activity. This study aimed to understand the influence of mental health, sociocultural pressures, body dissatisfaction, and self-efficacy on postpartum mothers’ reengagement in team sports. A cross-sectional study with 232 Australian mothers (M = 32.0, SD = 5.14) who had a biological child aged 0–3 years was conducted. A hierarchical multiple regression assessing body dissatisfaction found that the combined variables explained 31.8% of the variance in body dissatisfaction, with breastfeeding (b = −4.25), number of children (b = 1.90), depression (b = 29.38), and sociocultural pressures (b = 22.32) being significant. Body dissatisfaction was not directly associated with sport reengagement. However, a mediation analysis found that self-efficacy significantly mediated the relationship between body dissatisfaction and sport reengagement. Overall, this study suggests that to improve postpartum mothers’ engagement in sports, there needs to be a focus on building their self-efficacy for participating, such as through game adaptations or participation flexibility to suit their changing body and needs.