Prior tuberculosis infection is a susceptibility factor for subsequent infection by tuberculous and non-tuberculous mycobacteria. Tuberculous granulomas are a long-lasting histological hallmark of tuberculosis and are known to be inhabited by superinfecting tuberculous mycobacteria in TB patients and zebrafish models. We hypothesised tuberculous granulomas may provide a niche for the growth of the emerging opportunistic pathogen Mycobacterium abscessus. We find preferential growth of secondary M. abscessus infection inside primary Mycobacterium marinum granulomas recapitulating the predisposing effect of tuberculous mycobacterial infection to infection by non-tuberculous mycobacteria. Using optically transparent zebrafish embryos we define the host and bacterial factors responsible for colonisation revealing a potentially clinically important host niche for non-tuberculous mycobacterial growth in a vulnerable patient population.