Direct studies of mammalian carnivores are challenging due to the animals' secretive nature and the high costs associated with their capture and handling. Use of noninvasive hair sampling to survey these reclusive species has great potential as an alternative, with wide applicability in ecology and conservation. Hair-trapping has been extensively used for focal studies of temperate mammals, but its use and applicability as a means to survey mammals in tropical environs has never been addressed. We evaluated the effectiveness of 2 hair-trap types and 2 scents along an elevational gradient within El Cielo Biosphere Reserve (ECBR, Mexico) to detect presence of carnivores. Hair-traps that used roofing nails as a hair-collecting surface collected more hairs and detected a greater number of species than did hair-traps that used velcro strips. Different scent treatments (commercial fragrance and catnip oil) did not differ for these same variables. Of successful nail hair-traps, 60% collected ≥20 hairs (max. = 439), providing enough material for DNA analyses. Hair-trap surveys detected 74% of the potential target mammal species at ECBR with only 19 days of field effort. Developing countries have limited budgets for biodiversity monitoring and hair-traps compare favorably with other methods with a high cost–benefit ratio. Hair-traps are inexpensive, portable, can be made with over-the-counter materials, and can be successfully used to collect data applicable to population and genetic studies of tropical carnivores.