Although it may seem paradoxical, primary care and mental health professionals develop prejudices and discriminatory attitudes towards people with mental health problems in a very similar way to the rest of the population. The main objective of this project was to design, implement and evaluate two awareness interventions respectively tailored to reduce stigma and discrimination beliefs and attitudes towards persons with a mental health diagnosis among primary care (PC) and mental health (MH) professionals. These interventions were developed by Obertament, the Catalan alliance against stigma and discrimination in mental health. The TLC3 (Targeted, Local, Credible, Continuous Contact) methodology was adapted to the Catalan PC and MH professional contexts. Activists with lived experience of mental health diagnosis carried out awareness-raising interventions in PC and MH health centres. The efficacy of these interventions was evaluated using two prospective double-blind cluster-wait-list-randomized-controlled trial experimental designs. Stigmatizing beliefs and behaviours were measured with the Opening Minds Stigma Scale for Health Care Providers in primary care centres and with the Beliefs and Attitudes towards Mental Health Service users’ rights in mental health centres. Positive reductions in both PC and MH professionals’ stigmatising beliefs and attitudes were found in the 1-month follow-up, although a ‘rebound effect’ at the 3-month follow up was also detected. This emphasizes the importance of the continuity of the presence of anti-stigma activities and messages. Attrition rates where high, which can hamper the reliability of the results. Further follow-up studies should enquiry effects of long-term interventions aimed at reducing stigmatising beliefs and attitudes among primary care and mental health professionals.