Nickel (Ni) is a moderately toxic metal emitted primarily by vehicular and industrial activities, with well-documented associations with allergic and respiratory effects. This study presents novel data on Ni bioaccumulation in wild mushrooms from urban parks in Leicester, the UK, and compares these findings with previous Ni data from native mosses used as passive biomonitors in the same locations. A total of 106 mushrooms from 14 species were collected and analysed for Ni by ICP-MS following acid digestion. Due to a limit of detection (LoD) of 3.40 mg/kg dry weight, 56.8% of values were censored. Among detectable samples, Ni concentrations ranged up to 90.50 mg/kg dw, with Coprinus atramentarius and Mycena citrinomarginata showing the highest mean values (56.36 and 17.40 mg/kg dw, respectively). By contrast, Agaricus bitorquis and Marasmius oreades showed no detectable accumulation (mean < 3.40 mg/kg). Spatially, elevated Ni levels were observed in mushrooms from parks located near high-traffic zones such as Abbey Park and Narborough Road. While previous moss-based studies revealed strong correlations between ambient Ni deposition and traffic exposure, mushroom Ni levels appeared more influenced by species-specific uptake capacity and root-zone exposure, rather than surface deposition alone. Notably, some areas with high Ni in mosses yielded mushrooms with low or non-detectable concentrations, indicating differences in exposure pathways and biological accumulation mechanisms. Although no regulatory thresholds exist for nickel in mushrooms, the concentrations detected in the wild edible species collected were relatively low. Human health risk assessments indicated no concern for occasional mushroom consumers. This study demonstrates the complementary value of active (fungi) and passive (moss) biomonitoring and highlights the importance of integrating multiple organism types when evaluating urban environmental pollution.