<ns4:p><ns4:bold>Background</ns4:bold>: This study seeks to determine the extent of women's out-of-pocket (OOP) payments for delivery under the free maternity policy (FMP). </ns4:p><ns4:p> <ns4:bold>Methods</ns4:bold>: We conducted a convergent parallel mixed-methods study using quantitative and qualitative data collection. The study was set in three facilities (levels 3, 4, and 5) in Kiambu County, Kenya. The study involved exit interview (EI) surveys with mothers (n = 553) who utilised FMP delivery services and focus group discussions (FGDs) with mothers who returned for postnatal visits (6, 10, and 14 weeks). There were 21 in-depth interviews (IDIs) with county officials and healthcare workers (HCWs). Quantitative data were analysed using descriptive statistics, while qualitative data were audio-recorded, transcribed and analysed using thematic analysis. </ns4:p><ns4:p> <ns4:bold>Results</ns4:bold>: Despite the FMP being free on paper, mothers incurred OOP payments in practice. The overall mean OOP payments incurred by mothers who underwent normal delivery was 9.50 USD (SD 8.20 USD), and caesarean section (CS) was 10.88 USD (SD 15.16 USD). The main cost drivers were transport, lack of adequate supply and medications, lack of policy clarity by health workers, failure to notify the NHIF office of available clients, and ultrasound scan services. While the OOP payments were not deemed catastrophic, some women perceived it as a barrier to care as they ended up using savings or selling their assets to meet the costs. There were no patient characteristics associated with OOP payments. </ns4:p><ns4:p> <ns4:bold>Conclusions</ns4:bold>: OOP payments during childbirth in Kenya place a considerable economic burden on mothers and their households. There is need to promote awareness of the policy and provide a sustainable form of transport, especially during emergencies, through collaboration with partners. Prioritising the supply of required medication used in maternal services in the universal health care benefits package to which Kenyan citizens are entitled, or sustainably financing the FMP is crucial.</ns4:p>