Stable carbon (¹³C/¹²C; δ¹³C) and nitrogen (¹⁵N/¹⁴N; δ¹⁵N) isotope ratios are best used to assess wild animal diets when the isotopic differences between consumers and diets are known. These differences are called discrimination factors (expressed with Δ notation). We report the 1st Δ¹³C and Δ¹⁵N values between diet and fur from captive individuals held on controlled diets for 7 months and representing 4 felid species: African lions (Panthera leo), bobcats (Lynx rufus), Canada lynx (Lynx canadensis), and mountain lions (Puma concolor). All animals were fed a mix of diet items (beef, beef rib, a commercial carnivore diet, chicken, mice, rats, turkey, and turkey wings) that was consistent throughout their molting period. Weekly diet composition was determined by the percentage of mass of each diet item and overall δ¹³C and δ¹⁵N values were calculated for each animal's diet. The mean Δ¹³C and Δ¹⁵N values (± SD) between felid fur and their non–lipid-extracted diets were 1.1‰ ± 0.2‰ and 3.5‰ ± 0.0‰, respectively (African lion, n = 1 animal sampled at 2 intervals); 5.5‰ ± 0.5‰ and 4.1‰ ± 0.1‰, respectively (bobcats, n = 3); 2.4‰ and 3.3‰, respectively (Canada lynx, n = 1); and 4.7‰ ± 0.6‰ and 4.5‰ ± 0.2‰, respectively (mountain lions, n = 2). Variations in Δ¹³C and Δ¹⁵N values among species were likely due to dietary differences and we recommend the use of the Δ¹³C (5.5 ± 0.5) and Δ¹⁵N (4.1 ± 0.1) values obtained from the bobcats for future determinations of wild felid foraging ecology as they were held on diets composed of 100% whole animals and animal parts, which best reflects diets of wild felids.