Academic journals increasingly request a full disclosure of financial conflict of interest (CoI). The Committee for Publication Ethics provides editors with guidance about the course of action in the case of suspected non-disclosure. No prior study has examined the extent to which journal articles on psychosocial interventions disclose CoI, and how journal editors process requests to examine suspected undisclosed CoI. Four internationally disseminated psychosocial interventions were examined. 136 articles related to an intervention, co-authored by intervention developers and published in health sciences journals were retrieved as requiring a CoI statement. Two editors refused consent to be included in the study. COI disclosures and editor responses were coded for 134 articles. Overall, 92/134 (71%) of all articles were found to have absent, incomplete or partly misleading CoI disclosures. Disclosure rates for the four programs varied significantly between 11% and 73%. Journal editors were contacted about 92 published articles with no CoI disclosure or a disclosure that was considered problematic. In 65/92 (71%) of all cases the editors published an ‘erratum’ or ‘corrigendum’. In 16 of these cases the journal had mishandled a submitted disclosure. The most frequent reason for non-publication of an erratum was that the journal had no disclosure policy at the time of the publication (16 cases). Consumers of research on psychosocial interventions published in peer-reviewed journals cannot currently assume that CoI disclosures are adequate and complete. More efforts are needed to achieve transparency.