Adult coloring books have flooded the market with titles alluding to therapeutic value, yet it is unclear whether they fulfil that promise. Here, we tested whether adult coloring was related to improvements in psychological outcomes. Female university students (n = 104) were randomly assigned to a coloring intervention or a logic-puzzle control group. Participants completed an inventory of psychological measures (depressive symptoms, stress, anxiety, flourishing, resilience, mindfulness) and then participated in a 1-week intervention of either daily coloring or logic-puzzles. Following the intervention, participants again completed the inventory of psychological measures. Coloring participants showed significantly lower levels of depressive symptoms and anxiety after the intervention, but control participants did not. We conclude that daily coloring can improve some negative psychological outcomes and that it may provide an effective, inexpensive, and highly accessible self-help tool for nonclinical samples.