Over half of women with psychosis are mothers. Research suggests that mothers with psychosis face unique challenges affecting both their mental health prognosis and their relationship with their children. Moreover, those children have a higher risk of developing a mental disorder. Notwithstanding, interventions specifically tailored to these families remain largely uncovered. Metacognitive Training (MCT) has demonstrated its efficacy in improving cognitive insight, symptom management, and social cognition in people with psychosis. However, there is no evidence of the efficacy of MCT in a family setting (MCT-F). This study describes the first adaptation of MCT for mothers with psychosis and their adolescent children in an online group setting. The phases (assessment, decision, adaptation, production, topical experts’ integration) of the ADAPT-ITT model were systematically applied through a participatory approach (n = 22), including a first-person perspective and involving qualitative (e.g., topical expert literature review and consensus groups, interviews, thematic analyses) and quantitative methods. While MCT’s core components were retained, participants guided adaptations both in content and delivery. The findings suggest the importance of community engagement and sharing decision-making processes to demonstrate the acceptability and feasibility of the adapted intervention. Employing a structured approach such as the ADAPT-ITT model ensures readiness of the new training for efficacy trials.