Participatory art projects for people with mental health needs typically claim outcomes such as improvements in confidence, self-esteem, social participation and mental health. However, such claims have rarely been subjected to robust outcome research. This paper reports outcomes from a survey of 44 female and 18 male new art project participants attending 22 art projects in England, carried out as part of a national evaluation. Outcomes were quantified through self-completed questionnaires on first entry to the project, during January to March of 2006, and 6 months later. The questionnaires included three measures: empowerment, mental health [Clinical Outcomes in Routine Evaluation (CORE)] and social inclusion. Paired t-tests were used to compare overall change, and mixed model repeated measures analysis of variance to compare subgroups, including age, gender, educational level, mental health and level of participation. Results showed significant improvements in empowerment (P = 0.01), mental health (P = 0.03) and social inclusion (P = 0.01). Participants with higher CORE scores, no new stress in their lives and positive impressions of the impact of arts on their life benefited most over all three measures. Positive impressions of the impact of arts were significantly associated with improvement on all three measures, but the largest effect was for empowerment (P = 0.002) rather than mental health or social inclusion. This study suggests that arts participation positively benefits people with mental health difficulties. Arts participation increased levels of empowerment and had potential to impact on mental health and social inclusion.