Earthworm consumption and egestion of organic materials can increase bioavailable nitrogen in soils. Along with other benefits resulting from their burrowing activities, this process can increase soil fertility. This research investigated whether earthworms were present, and whether a relationship between earthworms and increased ammonium and nitrate levels was seen in the soils of the agricultural green roofs sampled in the greater Toronto area. Earthworms were found at several of the agricultural green roofs, but low soil moisture, low organic carbon, shallow depth, and compactness may have inhibited the establishment of earthworm populations in some soils. Results showed a statistically significant increase in levels of ammonium, but not in nitrate, with the increasing presence of earthworms. Findings indicate that some degree of increased bioavailable nitrogen benefits, resulting from earthworm presence, that are evident in conventional agricultural soils, can also be possible in agricultural green roofs, with attention to management of soil conditions that support earthworm populations.