This study explores the use of dog bone as a substitute for human bone when investigating past diet using 13C/12C and 15N/14N in collagen and 13C/12C in apatite, for ancestral Huron-Wendat communities in southern Ontario (1300–1650 CE). Canid bones from five Huron-Wendat sites in southern Ontario were analyzed and compared to faunal isotope values from these and other geographically proximate sites, and previously published human stable isotope values associated with four of the Huron-Wendat village sites. Evidence from bone collagen and bone apatite suggest that maize, a staple of ancestral Huron-Wendat diet, is clearly present in the diet of these ancient dogs. Carbon isotope compositions (i.e., δ13C) for dogs and humans correspond well through time, suggesting that dogs can serve as proxies for contemporary human maize consumption. Dog nitrogen isotope compositions are consistently lower than human values (on average <2‰ lower), and show greater overall variability, so δ15N values need to be established for each archaeological context independently. This evidence is framed with knowledge from ethnographic sources and oral tradition on Huron-Wendat dog ecology that demonstrates a mutualistic symbiosis based on companionship, shelter, and food.