Abstract Background Female officers and staff face gender-specific challenges, particularly, during pregnancy and motherhood. Our study explores whether and how motherhood affects mental health outcomes (e.g., probable depression and anxiety) and return to work following sickness absence (SA), considering mediating role of workplace social support. Methods Logistic regression analysed probable depression and anxiety using Airwave Health Monitoring Study (AHMS) data. Cox proportional hazards models assessed return to work after sickness absence, linking AHMS with sickness absence data from 26 police forces. Exposure variables were created by the interaction of motherhood status and social support, while covariates included sociodemographic, lifestyle, and work-related factors. Results Mothers with low social support from superiors had higher odds of probable depression (OR = 2.14, 95% CI = 1.81-2.54) and anxiety (OR = 1.86, 95% CI = 1.62-2.14) compared to non-mothers. Moderate and high social support reduced odds of depression (Moderate: OR = 0.97, 95% CI = 0.85-1.11; High: OR = 0.65, 95% CI = 0.57-0.73) and anxiety (Moderate: OR = 1.24, 95% CI = 1.12-1.36; High: OR = 0.82, 95% CI = 0.75-0.9) for mothers, but the impact varied when adjusted for covariates. Mothers with lower levels of social support were less likely to return to work after SA compared to non-mothers, as indicated by the survival analysis (Low social support: HR = 0.83, 95% CI = 0.95-1.13; High social support: HR = 1, 95% CI = 0.96-1.04). These trends persisted across social support sources-colleagues and combined support-emphasising the complex interplay between workplace social support, motherhood, mental health, and sickness absence in policing. Conclusions Our study emphasises boosting workplace social support for female police officers and staff, to aid them in navigating motherhood demands. This improvement can lead to better mental health, retention, job satisfaction, and organisational effectiveness, ultimately promoting community safety. Key messages • Highlighting the importance of workplace social support for female police officers and staff, informs policy makers and practitioners to prioritize social support initiatives within policing. • Lower social support was associated with a reduced likelihood of returning to work after sickness absence, particularly among mothers compared to non-mothers.