Large carnivore populations are recovering in many protected areas in North America, but the effect of increasing carnivore numbers on existing predator–prey and predator–predator interactions is poorly understood. We studied diet and spatial overlap among cougars (Puma concolor) and gray wolves (Canis lupus) in Banff National Park, Alberta (1993–2004) to evaluate how wolf recovery in the park influenced diet choice and space use patterns of resident cougars. Cougars (n =13) and wolves (n= 8 in 2 packs) were monitored intensively over 3 winters (2000–2001 to 2002–2003) via radio telemetry and snowtracking. We documented a 65% decline in the local elk population following the arrival of wolves, with cougars concurrently switching from a winter diet primarily constituted of elk to one consisting mainly of deer and other alternative prey. Elk also became less important in wolf diet, but this latter diet switch lagged 1 y behind that of cougars. Wolves were responsible for cougar mortality and usurping prey carcasses from cougars, but cougars failed to exhibit reciprocal behaviour. Cougar and wolf home ranges overlapped, but cougars showed temporal avoidance of areas recently occupied by wolves. We conclude that wolves can alter the diet and space use patterns of sympatric large carnivores through interference and exploitative interactions. Understanding these relationships is important for the effective conservation and management of large mammals in protected areas where carnivore populations are recovering.