Objectives The primary objective of this study was to examine the effects of one-session physical or mindfulness training on university students' mood, attention and executive functions in two separate randomized studies. Methods Study 1 (physical activity intervention) was implemented in a seminar with 63 and Study 2 (mindfulness intervention) in another seminar with 28 university students. The physical intervention included stretching exercises, balancing tasks, and medium intensity cardiovascular activities. The mindfulness training included yoga exercises, guided attention, and a body scan. In the control conditions, students watched a 15-min fitness or yoga video, respectively. Several mood and attention scales, as well as executive functions were assessed before and after the intervention or control activity. A randomized within-subject cross-over design was applied in both studies. Results Repeated-measures analysis of variance revealed that participants in both intervention conditions reported mood to be more positive, more awake and calmer after the intervention compared to the control conditions. These effects were medium to large (Study 1: eta(2) = .08-.30, Study 2: eta(2) = .15-.30). Attention scores improved more relative to the control condition after the physical intervention (medium effect size, eta(2) = .11). Executive function scores improved more relative to the control condition after the mindfulness intervention (medium effect size, eta(2) = .17). Conclusions These results indicate that a short bout (15-min) of physical or mindfulness activity in a university learning setting positively affected dimensions of mood and cognition known to support academic learning.