Red and sugar maple leaves collected in the summer and fall from Canada, were evaluated for phenolic content, antioxidant, ${alpha}$-glucosidase, and ${alpha}$-amylase inhibitory activities variation. The phenolic contents of summer red maple leaves (RML-S) and summer sugar maple leaves (SML-S) were higher than red and sugar maple leaves collected in fall (RML-F and SML-F, respectively). HPLC analyses showed differences in phenolic compounds present in the SML samples compared to the RML samples. The extracts were assayed for yeast and rat ${alpha}$-glucosidase inhibitory activities. Both results showed that SML-S extracts had the highest inhibitory activity which could possibly be attributed to the unique phenolics present therein. Milder effects were observed in terms of ${alpha}$-amylase inhibitory activity, with RML-F having the highest inhibitory activity. These results suggest that maple tree leaf extracts may have potential for phenolic-mediated ${alpha}$-glucosidase inhibition, relevant to type 2 diabetes management, with SML-S extract having the highest bioactivity.