BACKGROUND: There are several barriers that may hamper adolescent mothers' utilization of available health interventions for perinatal depression. Innovative treatment approaches are needed to increase adolescent mothers' access to mental health care for improved maternal and child health outcomes. Mobile phones have the potential to serve as important conduits to mental health care in Africa. However, mobile phone use patterns and needs among young mothers in Nigeria are not well documented. OBJECTIVE: This study sought to determine the prevalence of mobile phone use among perinatal adolescents and report patterns of use, as well as to assess the openness of young mothers to mobile health (mHealth) mental health interventions. METHODS: We surveyed 260 adolescent mothers (ages 16-19 years) in their perinatal or postnatal periods of pregnancies in 33 primary health care clinics in Ibadan, Oyo State, Nigeria in 2020. Respondents were included if they were pregnant with a gestation age of greater than or equal to 4 weeks, or had babies (which they had birthed) that were younger than 12 months. RESULTS: The total study sample consisted of 260 adolescent mothers with a mean age of 18.4 (SD 0.88) years. The majority of the respondents (233/260, 89.6%) owned mobile phones (eg, keypad, keypad and internet, smartphones); 22 (8.5%) of the 260 mothers had access to phones that belonged to relatives who lived in the same household, while 5 (1.9%) had access only to public paid phones. Only 23% (54/233) of phone owners (which is 20.5% of the total study population) had smartphones. On average, respondents reported first using mobile phones at 15.5 (SD 2.06) years old. The majority of respondents (222/260, 85.4%) reported using their phones for an average of 45 minutes daily for calls to family members. Facebook was the social media platform that was most often used among respondents who had phones with internet access (122/146 minutes per day, 83.4%). The majority of the sample responded as being "interested" and "very interested" in the use of mobile phones for preventive interventions (250/260, 96.2%) and treatment (243/260, 93.5%) information on mental illness such as depression and "hearing voices." Half of the respondents (126/233, 50.4%) preferred to receive such information in the form of text messages. CONCLUSIONS: Findings from this study suggest that the vast majority of perinatal adolescents in Nigeria own and use mobile phones and that they are interested in leveraging these devices for prevention, treatment, and informational campaigns focused on mental health. The use of smartphones in this population is relatively low, and health intervention through text messages were favored by the women.