Background: Equitable health care utilization is a pillar of the Universal Health Coverage (UHC) and is also a concern to policymakers. Measuring and quantifying the inequalities are essential in assessing the progress toward achieving the UHC goals. Several studies have focused on overall measures of unfair inequality in health care utilization. The overall approaches to outpatient and inpatient services are not representative of the differences in health care usage in public and private sectors in a mixed healthcare system, like Iran. A few studies have assessed inequality measures for general practitioners (GPs), specialists (SPs), and hospital admission services in different sectors, separately. Objectives: This study aimed at measuring health care utilization inequalities in outpatient and inpatient health services in public and private sectors in Iran. Methods: In this study, national representative data derived from the utilization of health services survey (UHSS) in 2014 was used. The concentration curve (CC) and concentration index (CI) were applied to assess inequalities in health care utilization services, including the number of GP visits, SP visits, and admission in hospitals. We used ADePT software to produce a nonlinear estimation of CI for these count variables. The indirect standardization method was used to standardize the services for differences in needs by age and gender. The inequality in health care utilization was examined in both public and private sectors, separately. Results: Based on the results, public and private outpatient settings, except for the private GP visits, followed a pro-poor pattern. Inpatient admission in the public sector had a pro-poor model, but it showed a pro-rich pattern in the private sector. GP visits in the private sector changed in favor of the poorer people and SP visits in the public sector changed toward a pro-rich pattern after standardization for differences in needs. CI for family physician (FP) and GP visits in public and private sectors, and also SP visits in public and private sectors was -0.089, -0.086, -0.010, 0.025, and -0.018, respectively. CI for the inpatient admission in public and private sectors was -0.126 and 0.157, respectively. GP, SP and hospital services utilization showed a pro-poor pattern. Conclusions: The results of this study showed that most of the health care utilization followed a pro-poor model in the mixed health care system in Iran. SP visits in the public sector changed toward a pro-rich pattern after standardization for differences in needs. Although public outpatient services need more attention to maintain their pro-poor distribution, SP visits in the public sector should be more considered to follow a pro-poor pattern. Health policymakers are recommended to take measures to eliminate barriers to access this service. This may lead to reduce a gap between the poor and rich people in the utilization of the health care and moving toward the UHC.