The current study investigated the impact of the covid-19 pandemic on the psychological well-being of undergraduate students in Rivers State, Southern Nigeria. The study adopted the descriptive longitudinal research design with a sample of 108 students drawn using the convenience sampling technique. Using six research questions and corresponding null hypotheses, the study further ascertained the impact of the pandemic on the psychological well-being dimensions of autonomy, environmental mastery, personal growth, positive relations with other, purpose of life and self-acceptance. Data for the study was collected before and during the pandemic using traditional paper-and-pencil format and Google Forms® respectively. Collected data were analyzed using mean, standard deviation and mean difference to answer the research questions, while dependent sample t-test was used to test the corresponding null hypotheses. Result revealed that the COVID-19 pandemic had a significant negative impact on the psychological functioning of the students with the positive relations with others dimension having the greatest impact. On the basis of the result, it was therefore recommended that it is important for students to undergo psychological screening to ascertain their mental health functioning so as to provide them with support system to not only stabilize their psychological health, but also their improve their holistic functioning.