Continuous monitoring of ammonia (NH) in humid environments poses a notable challenge for gas sensing applications because of its effect on sensor sensitivity. The present work investigates the detection of NH in a natural humid environment utilizing ReS/TiCT heterostructures as a sensing platform. ReS nanosheets were vertically grown on the surface of TiCT sheets through a hydrothermal synthetic approach, resulting in the formation of ReS/TiCT heterostructures. The structural, morphological, and optical properties of ReS/TiCT were investigated using various state-of-the-art techniques, including scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, zeta potential, Brunauer-Emmett-Teller technique, and Raman spectroscopy. The heterostructures exhibited 1.3- and 8-fold increases in specific surface area compared with ReS and TiCT, respectively, potentially enhancing the active gas adsorption sites. The electrical investigations of the ReS/TiCT-based sensor demonstrated enhanced selectivity and superior sensing response ranging from 7.8 to 12.4% toward 10 ppm of NH within a relative humidity range of 15-85% at room temperature. These findings highlight the synergistic effect of ReS and TiCT, offering valuable insights for NH sensing in environments with high humidity, and are explained in the gas sensing mechanism.