Background: Mindfulness-based cognitive therapy (MBCT) has evidence of efficacy in a range of populations, but few studies to date have reported on MBCT for treatment of anxious and depressive symptoms in Parkinson's disease (PD). Aims: The aim of this study was to examine the efficacy of modified MBCT in reducing symptoms of anxiety and depression and improving quality of life in PD. Method: Thirty-six individuals with PD were randomly assigned to either modified MBCT or a waitlist control. Changes in symptoms of anxiety, depression and quality of life were compared at group level using generalized linear mixed models and at individual level using reliable change analysis. Results: At post-treatment, there was a significant reduction in depressive symptoms for people undertaking modified MBCT at both group and individual levels compared with controls. There was no significant effect on anxiety or quality of life at the group level, although significantly more people had reliable improvement in anxiety after modified MBCT than after waitlist. Significantly more waitlist participants had reliable deterioration in symptoms of anxiety and depression than those completing modified MBCT. Most participants stayed engaged in modified MBCT, with only three drop-outs. Discussion: This proof-of-concept study demonstrates the potential efficacy of modified MBCT as a treatment for depressive symptoms in Parkinson's disease and suggests further research is warranted.