To assess the availability, accessibility, appropriateness and quality of adolescent sexual and reproductive health (ASRH) services in primary health care (PHC) facilities in Plateau State, Nigeria, a cross-sectional study was conducted in 230 PHC facilities across the three senatorial zones of Plateau state. Primary data were obtained through face-to-face interviews with heads of facilities from December 2018 to May 2019. An adapted questionnaire from the World Health Organization (WHO) was used, covering five domains, to ascertain the extent that ASRH services were available and provided. Very few PHC facilities in the state had space (1.3%) and equipment (12.2%) for ASRH services. The proportion of PHC facilities offering counselling on sexuality was 11.3%, counselling on safe sex was 17%, counselling on contraception was 11.3% and management of gender-based violence was 3%. Most facilities were not operating at convenient times for adolescents. Only 2.6% PHC facilities had posters targeted at ASRH and just 7% of the PHCs had staff trained on ASRH. These findings underscore that the majority of PHC facilities surveyed in Plateau State, Nigeria, lacked dedicated space, basic equipment, and essential sexual and reproductive health care services for ASRH, which in turn negatively affect general public health and specifically, maternal health indices in Nigeria. Structural changes, including implementation of policy and adequate additional training of healthcare workers, are necessary to effectively promote ASRH.