Background: There is an emerging evidence base that mindfulness for psychosis is a safe and effective intervention. However, empirical data on the within-session effects of mindfulness meditation was hitherto lacking. Aims: The aim of the study was to assess the impact of taking part in a mindfulness for psychosis group, using a within-session self-report measure of general stress, and symptom-related distress. Method: Users of a secondary mental health service (n = 34), who experienced enduring psychotic symptoms, took part in an 8-week mindfulness for psychosis group in a community setting. Mindfulness meditations were limited to 10 minutes and included explicit reference to psychotic experience arising during the practice. Participants self-rated general stress, and symptom-related distress, before and after each group session using a visual analogue scale. Results: Average ratings of general stress and symptom-related distress decreased from pre- to post-session for all eight sessions, although not all differences were statistically significant. There was no increase in general stress, or symptom-related distress across any session. Conclusions: There was evidence of positive effects and no evidence of any harmful effects arising from people with psychotic symptoms taking part in a mindfulness for psychosis session.