Supportive policy and services environment for adolescent and young people’s sexual and reproductive health (SRH) is recently emerging in many African nations. The objective of this study was to assess the provision and experiences of care in SRH services for adolescents and young people (AYP) in a Nigerian setting. Twelve male and female mystery clients (MCs) conducted 144 visits at 27 selected primary and secondary health facilities in two Local Government Areas (LGA) in Ogun State, Southwest Nigeria. A 27-item adolescent quality of care (AHQOC) index obtained after factor analysis, and with Cronbach’s Alpha of 0.7 was used to obtain a quality-of-care score for each clinic visit. Linear panel-data random-effects regression models using the generalized least square (GLS) estimator were used to assess quality associated factors. A sentiment analysis was done on the qualitative narrative summaries provided by MCs after each visit. There was an absence of the use of educational materials during the majority of the visits (only 39.6% used). The MCs' medical history (90.3%), social record (63.9%), sexual/reproductive history (53.5%), or contraceptive experience (66.0%) were not obtained in most of the visits. Female MC visits had a lower AHQOC index rating on average compared to males (β=-0.3, CI -1.4 – 0.9 p=0.635), rural health facilities had a lower AHQOC index rating on average compared to urban (β=-2.7, CI -4.7 – -0.6, p=0.011), and a higher ranking of the health worker on the scale of 1-10 corresponded to a higher AHQOC index of the MC visit (β=1.9, CI 1.6 – 2.1, p<0.001). There were more positive than negative sentiments about the clinic encounters. This study found gaps in competencies of the health workers, and use of educational materials in clinic encounters with young people, as well as differential perception of quality of care by male and female AYPs.