We present a database of indigenous and non-indigenous terrestrial mammal records on Western Australian (WA) islands, updated from a database we published more than 20 years ago. The database includes records of 88 indigenous species on 155 islands, compared with 54 indigenous species on 141 WA islands in the paper by Abbott and Burbidge in CALMScience, Volume 1, pp. 259–324. The database also provides 266 records of 21 species of non-indigenous mammal species on 138 WA islands, more than double the number of records in the earlier review. Of the 33 threatened and near-threatened WA non-volant mammals, 16 occur naturally (and have persisted) on WA islands, five additional species occur on islands outside WA, 14 successful conservation translocations of 10 species have been undertaken to WA islands, and six species have been successfully translocated to 12 islands outside WA – two of which do not currently occur on WA islands. The house mouse now accounts for the largest number of extant records of non-indigenous species. Even with the increasing number of conservation translocations to mainland islands (fenced exclosures), WA islands remain essential for the effective conservation of several threatened and near-threatened mammals and many of the translocations to mainland islands have been sourced from islands.