While mindfulness intervention research is prevalent, it is limited in (1) relation to college students' grade point average (GPA) and retention and (2) minimum dosage recommended for the intervention. This repeated-measures quasi-experimental nonequivalent control groups study investigated differences in mindfulness, stress, flourishing, GPA, and retention between students (n = 248) in first-year experience seminars who received a brief mindfulness intervention and the comparison group (n = 125) who did not receive the intervention. The intervention consisted of three- to five-minute mindfulness exercises at the beginning of class that met once a week. In contrast to results of previous studies, this study--when controlling for class sections and gender--showed no significant differences in any outcome variable between groups. These results provide important evidence that a mindfulness dosing limit might exist. A post hoc binary logistic regression supported previous findings that GPA predicts retention. Implications are discussed in regard to college administrators, faculty, and student affairs professionals.