The provision of comprehensive sexuality education (CSE) accords opportunities for scientifically accurate information about sexual and reproductive health (SRH). We used a mixed-methods study to characterise adolescent SRH knowledge, attitudes and service utilisation experiences in the context of CSE implementation in Zambia. In-school young people aged 12–24 years (N = 1,612) in the North-Western Province were randomly surveyed. A 29-item index was constructed to measure alignment of knowledge, attitudes and values (KAV) with the CSE curriculum. Logistic regression, stratifying by sexual debut status, modelled associations of past-year HIV counselling and testing and family planning service access, respectively, with CSE-KAV index scores. Focus group discussions further explored perceptions of and experiences accessing SRH services. Despite moderate SRH knowledge and acceptability of SRH services, fewer than half of sexually experienced young people reported accessing SRH services. Among sexually experienced youth, neither HIV testing nor family planning service utilisation in the previous year were associated with higher CSE-KAV index scores. Salient barriers to SRH service uptake included limited perceived benefits, unsupportive household and community environments, and negative interactions with health providers. To increase accessibility and uptake of youth SRH services, linking school-based CSE to SRH services is recommended.