PURPOSE: Intervention development guidelines suggest that behavioural interventions benefit from being theory-based. Minority populations typically benefit less from asthma self-management interventions, and the extent to which appropriate theory has been used for culturally tailored interventions has not been addressed. We aimed to determine theory use and theoretical domains targeted in asthma self-management interventions for South Asian and Black populations. METHODS: We systematically searched electronic databases, research registers, manually searched relevant journals and reference lists of reviews for randomised controlled trials of asthma self-management for South Asian and Black populations, and extracted data using the Theory Coding Scheme to inform if/how theory was used and explore its associations with asthma outcomes, and the Theoretical Domains Framework was used to identify targeted theoretical domains and its relationship to effectiveness of asthma outcomes. RESULTS: 20 papers (19 trials) were identified; theory was not extensively used in interventions. It was unclear whether theory use or theoretical domains targeted in interventions improved asthma outcomes. South Asian interventions included 'behavioural regulation', while 'reinforcement' was mostly used in African American interventions. 'Knowledge' was central for all populations, though there were differences related to 'environmental context and resources' e.g., language adaptations for South Asians; asthma resources provided for African Americans. Author descriptions of interventions targeting providers were limited. CONCLUSIONS: There was little evidence of theory-based approaches used in cultural interventions for asthma self-management. Demystifying theoretical concepts (and cultural interpretations of constructs) may provide clarity for 'non-experts', enabling mainstream use of theory-driven approaches in intervention development.