Outside of pest control reports, little attention has been paid to interior ecosystems in high-latitude regions. Opportunistic sampling of live arthropods captured inside the University of Alaska Museum Fairbanks, Alaska, United States of America allowed us to describe and analyse one such interior ecosystem. We document a minimum of 77 arthropod species over 18 years. Beetles, spiders, and booklice represented 80% of the total abundance. Of those captured, synanthropes consisted primarily of fungivores and detritivores, seasonals consisted primarily of predators and omnivores, and transients consisted primarily of predators and had greater diet and species diversity than the synanthropes and transients. January was the most common month for capturing synanthropes, September for capturing seasonals, and July for capturing transients. Four synanthropic species not previously known from Alaska, which appear to have breeding populations inside the museum, were found: Dorypteryx domestica (Smithers, 1958) (Psocodea: Psyllipsocidae), Cartodere constricta (Gyllenhal, 1827), Dienerella filum (Aubé, 1850), and Corticaria serrata (Paykull 1800) (Coleoptera: Latridiidae). Three transient and one synanthrope species previously unreported from Alaska, with no evidence of breeding populations, were also found: the click beetle Danosoma obtectum (Say, 1839) (Coleoptera: Elateridae), a spider in the genus Phantyna, probably the species P. bicornis (Emerton, 1915) (Araneae: Dictynidae), two Colobopsis sp. ant specimens (Hymenoptera: Formicidae), and the synanthropic spider Oecobius cellariorum (Dugès, 1836) (Araneae: Oecobiidae).