Background/Aims Problems related to sexual health can have adverse effects on the overall health of adolescent girls, including those living with a physical disability. Improving sexual and reproductive health knowledge among this population can enable them to make informed decisions in relation to their sexual health. However, the sociodemographic characteristics that influence knowledge in this population have not been explored. This study investigated the influence of sociodemographic characteristics on the sexual and reproductive health knowledge of adolescent girls living with physical disabilities in Kiambu County, Kenya. Methods A cross-sectional mixed method study was conducted among 144 purposively selected adolescent girls aged 10–19 years old living with physical disabilities. A semi-structured questionnaire was used to gather data on participants' sociodemographic characteristics and their sexual and reproductive health knowledge. Odds ratios and logistic regression was used to analyse the data. Results One in five (20.8%) of the participants had already had a sexual experience, and only 24.3% of participants had good sexual and reproductive health knowledge. The majority of the participants (54.9%) had low socioeconomic status, which was the only factor significantly associated with level of knowledge (odds ratio=4.91, P=0.021). Conclusions Socioeconomic status is a major determinant of sexual and reproductive health knowledge among adolescent girls living with disabilities. Measures must be put in place to economically empower the families of these girls, to facilitate improved knowledge and thus ensure their sexual health and wellbeing. Implications for practice Education interventions are needed that are tailored to adolescent girls living with disabilities to promote reproductive health in this population.