INTRODUCTION: The objective of this study was to examine the effect of patient financial penalties on appointment nonadherence within a single academic institution's obstetrics and gynecology outpatient clinics. METHODS: This retrospective policy effectiveness-implementation hybrid study included administrative data from all appointments at a single academic institution’s obstetrics and gynecology outpatient clinics from May 1, 2018, to April 30, 2022. Institutional review board approval was waived for this study. The department-wide patient financial penalty policy for appointment nonadherence was implemented on May 1, 2020. We conducted an interrupted time series analysis after stratifying by insurance (Medicaid versus all insurance). Poisson regression was used to calculate incidence risk ratios (IRRs) with 95% CIs. RESULTS: There were 414,006 obstetrics and gynecology outpatient clinic appointments (pre-implementation [pre]: 208,696; post-implementation [post]: 205,410). Of these, 58,473 (14.1%; pre: 29,533 [14.2%]; post: 28,940 [14.1%]) appointments were not attended. Compared to the all insurance group, Medicaid patients had a higher rate of appointment nonadherence (36,872/188,343 [19.6%]; pre: 18,070 [19.6%]; post: 18,802 [19.6%]). In the all insurance group, the implementation of financial penalties resulted in a 4% increase in nonadherence (IRR 1.04 [95% CI, 0.99–1.09]). In the Medicaid group, the implementation of financial penalties did not change nonadherence (IRR 1.00 [95% CI, 0.98–1.02]). There was no significant difference in the coefficient between Medicaid and all insurance groups (P>.05). CONCLUSION: Institutional implementation of patient financial penalties for appointment nonadherence did not change appointment nonadherence rates in obstetrics and gynecology outpatient clinics. The lack of change persisted after stratifying by insurance despite the inability to charge Medicaid patients a financial penalty for appointment nonadherence.