Aims: This article examines how the Diderichsen model has been used and adapted in research on health inequalities during COVID-19, and explores how the pandemic has prompted further theoretical development. This review therefore addresses the question of how a well-established theoretical framework has helped researchers understand pandemic-related health inequalities and what opportunities exist for its continued refinement. Methods: A narrative literature review was conducted using Google Scholar, Web of Science, PubMed and Scopus. Included studies cited a key publication presenting the Diderichsen model and addressed COVID-19 as a central topic. After screening 298 articles, 24 were included for full analysis. The studies were categorised by how they engaged with the model - conceptually, empirically or through further development. Results: The Diderichsen model was commonly used to frame discussions of health inequality or to interpret pandemic-related disparities in exposure, vulnerability and outcomes. Several studies emphasised occupational and housing-related exposure, class-based comorbidities and the unequal social consequences of COVID-19. A smaller number of studies proposed expanded frameworks, incorporating multilevel and temporal dimensions and introducing new mechanisms related to pandemic responses. These adaptations often focused on migrants, ethnic minorities and other particularly affected groups. Conclusions: The review confirms the ongoing relevance of the Diderichsen model in pandemic health inequality research. It argues that the model can be further strengthened by explicitly incorporating concepts of political decision-making, symbolic recognition and social justice. This would improve its capacity to capture the full complexity of health inequalities in times of crisis.