Racial/ethnic minoritized students are at an increased risk of psychological distress. Supporting these students by providing them with opportunities to flourish could positively impact their mental and social health, and academic performance. This study explored the impact of values affirmation writing (intervention) compared to neutral writing (control) on the mental and social health and academic performance of first year students from minoritized racial and ethnic backgrounds in STEM fields. A total of 69 students participated in the study and were randomized into one of two conditions: (1) values affirmation (n = 34); or (2) neutral writing (n = 35). Participants completed a pre-intervention survey that consisted of a demographic questionnaire and 9 scales measuring mental and social health outcomes. Students were then asked to complete 3 writing prompts, specific to their condition. Post-intervention, participants completed the same scales previously administered and self-reported their grade point averages. There was a significant interaction between time and condition on anxiety and belonging scores, such that values affirmation participants experienced a decrease in anxiety over time relative to control participants, and the neutral writing control condition participants experienced a decrease in belonging compared to the values affirmation intervention condition. Additionally, there was a significant main effect of time on loneliness scores, such that there was a decrease over time in loneliness for both conditions. Affirming one’s personal values can buffer against negative mental and social health outcomes among minoritized students and highlight the potential for values affirmation interventions to have a lasting positive effect through sustained reductions in anxiety and loneliness.