Arthropod diversity was assessed during a 1-year experimental study of newly-established mulch plots and a 2-year descriptive study that included a variety of urban landscapes in central Ohio. Samples were gathered year-round from mulch in close proximity to structures. Five arthropod classes were represented in mulch ecosystems: Diplopoda (millipedes), Insecta (insects), Crustacea (crustaceans), Chilopoda (centipedes), and Arachnida (spiders and their kin). Millipedes were the most prevalent group of invertebrates, comprising 45.7% of all arthropods, and they were present at 42% of the sites. Insects were represented by 11 orders, with ants being the most prevalent group (24.8%), followed by fly larvae (20.0%), beetles (19.8%), barklice (15.2%), and termites (13.3%). Isopods and centipedes comprised 13.3% and 5.4% of the total number of arthropods, respectively. Nine families of spiders were present in the mulch samples; all were non-web builders. Arthropods quickly invaded novel mulch plots; their numbers at one month and one year were not significantly different. Arthropod diversity was comparable in experimental and descriptive sites, though overall numbers of arthropods were significantly higher in the latter.