Background: Psychosocial factors including stress are determinants of wellbeing. However, there is a shortage of information about how these relationships were impacted by the COVID-19 pandemic among adults in Nigeria.Objectives: To determine the associations between wellbeing, and impact of the COVID-19 pandemic, psychological distress (anxiety and depression), and perceived social support among adults in Nigeria during the first wave of the pandemic.Methods: Wellbeing (assessed using the WHO Wellbeing Index) was the outcome variable while the explanatory variables included anxiety and depressive symptoms (assessed using the Hospital Anxiety and Depression Scale), perceived social support (assessed using the Multidimensional Scale of Perceived Social Support) and perceived impact of the pandemic (assessed using perceived disruptions of life-domains). Univariate and multivariate logistic regression models were used to assess the associations between the outcome and explanatory variables. The models were adjusted for sociodemographic profile (highest level of education, employment status and payment status).Results: Low self-perceived impact of the pandemic was significantly associated with higher odds of high wellbeing (AOR: 2.59; 95% CI: 1.69-3.95; p<0.001). Other factors associated with significantly higher odds of high wellbeing were high perceived social support (AOR: 2.40; 95% CI:1.78-3.22; p<0.001) and having tertiary education (AOR: 1.51; 95% CI: 1.07-2.13; p=0.020). In contrast, experiencing anxiety symptoms were significantly associated with lower odds of high wellbeing (AOR: 0.24; 95% CI: 0.14-0.41; p<0.001)).Conclusions: Measures for enhancing the wellbeing of adults resident in Nigeria may include strategies to ameliorate the impact of the pandemic, strengthening social support systems, and promoting optimal physical and mental health.