Birth companionship during facility-based childbirth has been recommended by the World Health Organization to improve maternal and newborn outcomes. However, limited evidence exists on how companionship affects women's experiences of mistreatment during childbirth and their mental health. To assess the characteristics of birth companionship during intrapartum care and examine its associations with women's experiences of mistreatment and postpartum anxiety and depression. We analysed cross-sectional data on 314 women who gave birth in six public health facilities in rural Sindh, Pakistan. Women were interviewed 42 days postpartum about their childbirth experiences and postpartum anxiety and depression. Multivariable regression models were used to examine associations between birth companionship, mistreatment, and postpartum anxiety/depression. Path analysis explored whether mistreatment mediated the relationship between companionship and postpartum anxiety and depression. Most women (83.1%) had a full-time companion in the labor room, with in-laws (44.6%) being the most common, followed by family members (26.1%) and friends (15.0%). Higher levels of companion support were associated with lower levels of mistreatment, particularly regarding non-confidential care, lack of supportive care, and ineffective communication. Women receiving low companion support were 2.86 times more likely to experience postpartum anxiety and depression compared to those receiving high support. Informational support emerged as the strongest protective factor against both mistreatment and postpartum anxiety/depression. Path analysis revealed that the effect of companion support on postpartum mental health was mediated by experiences of mistreatment during childbirth. Birth companionship, especially informational support, plays a crucial role in reducing mistreatment during childbirth and improving maternal mental health outcomes. These findings underscore the need for supportive policies and health system interventions that actively encourage the engagement of companions from a woman's personal network during labor and childbirth. Future research should explore strategies to optimize the role of birth companions in promoting respectful maternity care and maternal well-being.

Data Collection: In-person interviews were conducted by trained data collectors in privacy using structured questionnaires. Women were recruited at health facilities at the time of discharge, and information on their sociodemographic characteristics was collected. Their experiences of childbirth and mental health were collected at 42 days postpartum at their homes. Data were collected electronically using tablets. Data were analysed in Stata version 16.0