Flow is a desirable state of consciousness and absorption in an optimally challenging activity. Prior research has investigated individual differences in flow. The present study investigates flow by contrasting physical versus mental activities, using a mixed-methods, sequential explanatory design. The sample from the quantitative phase included 205 undergraduate university students assessed on measures of personality, difficulties in emotion regulation, and flow. The big-five traits intellect and conscientiousness, as well as the emotion regulation subscale “lack of emotional clarity” predicted flow during mental activities, but unexpectedly no variables significantly predicted physical flow activities. The second phase used semi-structured interviews with 10 participants. Analyses of the interviews helped further explain the statistical findings, revealing four main themes: role of stress, source of guilt, presence of others, and satisfaction and fulfillment. We conclude that flow is especially relevant in physical activities which have advantages over mental activities in opportunities to experience flow.