This study tested trait- and state-mindfulness and trait- and state-positive affect (PA) relations within a cross-sectional study (Study 1; N¼174 76% women Mean (SD)age¼24 (2.7) years) and a randomized controlled 4-session mindfulness intervention study (Study 2; N¼51 65.4% women Mean (SD)age¼25 (4.3) years). Study 1: levels of trait-mindfulness and trait-like PA were related as theorized only among participants with meditation experience. Study 2: Study 2 is a secondary analysis of a mindfulness intervention study [Tanay Lotan & Bernstein (2012). Salutary proximal processes and distal mood and anxiety vulnerability outcomes of mindfulness training: A Pilot preventive intervention. Behavior Therapy 43 492–505]. Unexpectedly reduced levels of trait-like PA were observed pre- to post-intervention across conditions. No significant between-group mean differences were observed post-intervention. However as expected change in trait-mindfulness from preto post-intervention predicted change in trait-like PA among the intervention but not control condition. Second levels of state-mindfulness during mindfulness meditation were positively related to levels of state-PA. The theoretical and applied implications of these findings for mindfulness and PA are discussed.