An association between Mycobacterium malmoense and underlying lung disease has been described. The purpose of this study was to further explore this relationship and in particular to identify any relationship between Coal Workers' Pneumoconiosis (CWP) and M. malmoense infection. Patient charts were reviewed of all patients who had a positive sputum or bronchoalveolar lavage for M. malmoense from 1999 to 2006 in a large district general hospital in South Yorkshire, UK. We also performed a literature review in search of this association; one case report was found. Four patients had positive sputum cultures for M. malmoense but only three of these fulfilled the ATS 1997 criteria for diagnosis of disease. Of these three patients, all had clinical and radiologic evidence of CWP. This study strengthens the evidence of a link between nontuberculous mycobacteria and underlying lung disease but more importantly highlights an association between M. malmoense and CWP which has been rarely reported and is poorly understood.