We examined scavenging on mule deer (Odocoileus hemionus) carcasses by puma (Puma concolor) in the Peninsular Ranges of San Diego County, California. Between January 2001 and October 2003, we placed 44 deer carcasses at 23 sites and used them to examine scavenging events. We also documented 2 additional deer carcasses, not placed as bait, that were scavenged by puma. Eight to 12 puma (6 males, 2 to 5 females, and 1 of unknown sex) scavenged 20 of 46 deer carcasses (43.5%) at 12 of the 25 sites. Six puma (4 males, 2 females) were captured 7 times at scavenging sites. We identified 7 scavenging puma (5 males, 2 females) through captures and telemetry, and 1 unmarked, scavenging male from a camera trap. The 7 telemetered puma that scavenged ranged in age from 11 months to 9 years, and each individual scavenged on 1 to 6 deer (mean = 2.3). Deer carcasses were found and scavenged by puma from 1 to 14 days (mean = 5 days) after deposition, when carcass conditions ranged from frozen and fresh to rotting and maggot-infested. Puma treated scavenged carcasses as they would their own kills, dragging carcasses to preferred sites, caching, depositing scats, and making scrapes in the area. However, puma did not always attempt to cache tethered carcasses. During fieldwork, we also discovered that 1 telemetered puma repeatedly visited a domestic livestock graveyard and scavenged on surface-discarded horse and cattle carcasses. Puma are known to be opportunistic predators, but our results indicate that they are opportunistic scavengers as well. Due to the propensity of puma to scavenge, it is likely that some perceived kills might be scavenging events. Frequent monitoring and timely field investigation of mortality signals detected from telemetered prey species will help investigators identify those events. Scavenging behavior should be considered when evaluating or predicting the effects of puma predation on prey species.