PurposeThe purpose of this study was to explore the relationship between smartphone addiction, mental health and sleep quality among undergraduate pharmacy students in a Nigerian public university.Design/methodology/approachA cross-sectional study was conducted among undergraduate pharmacy students in a Nigerian university. Data was collected using self-administered questionnaires, including Smartphone Addiction Scale-Short version, Patient Health Questionnaire, Generalized Anxiety Disorder Scale and Pittsburgh Sleep Quality Index. The data obtained were analyzed using descriptive statistics, the chi-square test and the Pearson correlation. Probability values less than 0.05 were considered statistically significant.FindingsA total of 410 undergraduate pharmacy students participated in the study, giving a response rate of 95.57%. The prevalence of smartphone addiction, depression and anxiety symptoms were 40.24%, 28.30% and 23.66%, respectively. Most students had poor sleep quality (96.10%). The prevalence of smartphone addiction had a moderate positive correlation with the severity of depression (r = 0.363, p < 0.01) and anxiety (r = 0.261, p < 0.01) symptoms. Nevertheless, smartphone addiction showed no connection with sleep quality (r = 0.022, p = 0.663).Research limitations/implicationsThe study was conducted in a single public university in Nigeria, hence this might limit its generalizability. The provision of mental health support within universities could help address the high prevalence of smartphone addiction, mental health issues and poor sleep quality.Originality/valueTo the best of the authors’ knowledge, this was the first study to examine smartphone addiction among pharmacy students in a resource-limited setting with multicultural and multiethnic groups.