Background Substantial improvements have been observed in coverage and access to maternal health services in Ethiopia. However, quality of care has been lagging behind. Therefore, the aim of the study was to assess quality of OptionB + in Mekelle Zone, Northern Ethiopia.Methods Facility based cross-sectional study involving both quantitative and qualitative methods was conducted from December 2016- January 2017. The quality of service delivery was assessed in 11 public health facilities in Mekelle. Data collection was conducted using facility audit, observation, and client exit interview check list to assess (Input-Process–Output) quality components. Similarly in-depth interview guide was used to gather qualitative data. Data were analyzed using SPSS version 21 software. Descriptive statistics were computed to summarize the study findings and triangulation was made with qualitative findings.Results Overall, 2 (16.7%) of study health facilities full filled all the three quality components but none in 3(25%). The input quality component was better than the others in which 4(33.3%) facilities were rated as good. The process and output quality components were judged as good in 3(25%) study health facilities.Conclusion Only 16.7% of facilities studied were achieved good quality with respect to the three predetermined quality components. Since, assessed items in each quality component were potentially easy to intervene; strengthening program monitoring needed by program managers at each level of the health facilities.