In the context of an already large treatment gap in South Africa, this study aimed to examine how Covid-19 and the related lockdown measures affected the availability, accessibility, quality, and continuity of mental health services in the Western Cape province in South Africa. A mixed-methods design was employed, using narrative surveys, quantitative surveys, and qualitative semi-structured interviews, with 17 public mental health providers, and secondary data from the District Health Information System. We analysed and combined the data using descriptive statistics, template analysis and methodological triangulation. Results showed that Covid-19 and the lockdowns had negative impacts on mental health service provision at all levels of care, such as reduced access to services, increased stigma and discrimination, disrupted medication supply, increased workload and stress for providers, and the closure of psychosocial and therapeutic services. Innovations used by providers to mitigate these impacts included telehealth, online training, peer support groups, and community outreach. The study concludes that Covid-19 and the lockdowns exposed and exacerbated the existing gaps and challenges in mental health service provision in South Africa. Key recommendations for policy formation and response to future pandemics in the public mental health sector include: classifying psychological treatments as essential services, establishing an intersectoral mental health emergency response plan, involving mental health care users in the development of pandemic responses, creating policies for managing health emergencies in psychiatric facilities, and increasing resources for the mental health sector in South Africa. These recommendations are relevant for South Africa and other LMICs in ensuring adequate mental health care during public health emergencies.