The northern tiger cat (Leopardus tigrinus) is one of Brazil’s least studied felids, with no published population density estimates. A potential key conservation unit for the species is Mirador State Park (MSP) in NE Brazil, an area that also hosts humans and domestic dogs. Therefore, we assessed the park’s importance in terms of tiger cat conservation and whether domestic dogs present a threat to the survival of this species. We established 52 camera trap stations at three sites and monitored them for a total of 5030 trap-days. We calculated population densities in MSP using spatial and nonspatial methods as well as relative abundances and extrapolated these results to the other protected areas and corridor that compose the northern portion of the Cerrado Biosphere Reserve. We conducted a population viability analysis for tiger cats in the park and assessed the potential impact of domestic dogs. The tiger cat density estimates were 0.12 and 0.25 individuals/km2 (nonspatial) and 0.087 and 0.11 individuals/km2 (spatial), whereas the relative abundances ranged from 0.124 to 2.168 individuals/100 trap-nights. The tiger cat population was estimated at 287 individuals, with an extinction probability of 0% within the next 100 and 1000 years, although only in scenarios involving mild to no disease outbreaks. Large outbreaks or habitat loss would be detrimental to species survival in the area. Domestic dogs were detected at 80% of the stations where tiger cats were observed. The threat of disease transmission by domestic dogs potentially impacts 65% of the park and appears to be the primary threat to the species in that location. The northern tiger cat population was estimated at approximately 700 individuals in the entire protected area of the northern savannas; the total population in these regions and the additional corridor of the Cerrado Biosphere Reserve could be up to 2000–3000 individuals. Our results provide the first published density estimates of tiger cats and confirm the potential threat of domestic dogs to this felid in Mirador, thereby confirming the park’s importance as a key area for tiger cat conservation and the need for conservation actions. Given the density and abundance of tiger cats in MSP as well as the park’s large area, compared with other locations in the northern savannas, MSP may be the most important site for the worldwide, long-term conservation of L. tigrinus.