Background: Mental health disorders are increasingly becoming a global concern among university students. The prevalence of depression, anxiety and stress among pharmacy students in Nigeria is unknown. Objective: This study sought to examine the occurrence of depression, anxiety and stress and associated sociodemographic factors among undergraduate pharmacy students in Nigeria. Methods: The study was an online-based cross-sectional descriptive survey conducted among students from seven pharmacy schools in Nigeria. Students were recruited via their class WhatsApp groups and a link to a Google Form was provided for those who agreed to participate in the study. Data were analysed using IBM Statistical Product and Services Solution for Windows version 21.0. Results: A total of 408 students out of approximately 3,068 students responded to the survey (response rate: 13.32%). The prevalence of depression, anxiety and stress was 44.6%, 63.5%, and 35%, respectively. Depression was found to be strongly correlated with stress (r=0.739, p<0.001) and anxiety (r=0.715, p<0.001). Depression, anxiety and stress scores significantly correlated with perceived academic performance and year of study. There was no significant association between gender, cigarette smoking, type of accommodation, and the levels of depression, anxiety, and stress. Conclusion: The prevalence of depression, anxiety and stress among pharmacy students responding to a survey in Nigeria was high. Students in lower years of study and those with perceived poor academic performance had higher levels of depression, anxiety and stress. More studies are needed to explore the causes of depression, anxiety and stress among pharmacy students.