During the outbreak of highly infectious COVID-19, the Nigerian Ministry of Health primarily emphasized preventive strategies such as personal hygiene, social distancing, and self-isolation. However, there was a notable lack of information addressing mental well-being and coping mechanisms from both the Nigerian government and other relevant agencies. Notably, social distancing and self-isolation are well-documented triggers for mental health problems. Our study aimed to identify the socio-demographic correlates of mental health problems among adults in South-South Nigeria during the COVID-19 lockdown restrictions. This cross-sectional descriptive survey involved 1240 respondents from this region who completed online questionnaires designed using the Kobo Toolbox. The questionnaire covered sociodemographic information and included standardized assessments for generalized anxiety disorder (GAD), anger disorder, and depression disorder. Specifically, the GAD-7 assessed GAD, Spielberger&rsquo;s State-Trait Anger Expression Inventory-2 assessed anger disorder, and the beck depression inventory assessed depression disorder. Our results revealed that 37% of respondents experienced mild depression, 29% reported mild anxiety, and 27% experienced minimal anger. Significant associations were found between depression and factors such as marital status, age, and education level (p < 0.001). Similarly, anger expression was significantly associated with family size, monthly income, age, and marital status (p < 0.001). Anxiety also exhibited significant associations with sociodemographic characteristics (p < 0.001) in the study. In conclusion, our study highlights that sex, educational level, income, and marital status are important sociodemographic determinants of mental health outcomes.