We present a checklist of the beetles known to occur in and on the oyster mushroom, Pleurotus ostreatus Fries. A total of 136 taxa from 30 families are presented in our checklist. Taxa included in the checklist are known throughout North America with emphasis on those occurring in the southeastern United States. Both adult and larval forms are presented in the checklist along with the type of fungal association, of which ≈ 60% are obligate mycetobionts. A total of 58 beetle taxa were summarized from existing published records, and 78 taxa are new additions from our studies. A discussion of fungi as microhabitats for beetles is given using P. ostreatus and polyporoid fungi as examples.