Rates of anxiety and depression on college campuses are rising at an unprecedented rate. Analyzing longitudinal survey data and academic records from undergraduate students at a large public research university in the United States, this paper investigates the effects of mental health on college students’ academic achievement. Specifically, we first explore how anxiety and depression impact GPA and credit hours completed during a given semester. We then assess the long-term effect of pass/fail grading flexibility during the COVID-19 pandemic on the relationship between mental health and GPA. Through our results, we find that both anxiety and depression decrease GPA and credit hours completed each semester, with depression generally having larger effects. Additionally, pass/fail grading has a negative impact on future GPA, with these negative effects exacerbated for individuals experiencing anxiety and depression. We find no heterogeneity in the relationship between mental health and achievement by race, social support, and coping mechanisms, but do observe that the effects of mental health are less severe for first-generation and Hispanic students.