Nitrate (NO₃^-) contaminated groundwater has increased worldwide owing to anthropogenic activities such as the overuse of nitrogen-based fertilizers and discharge of poorly-treated wastewater. In this study, a novel Pd-In bimetallic catalyst supported on kalinite-induced zeolite (ZK) was developed for highly enhanced nitrate conversion into nitrogen gas. However, only a few studies have investigated the effect of natural substances in real groundwater on catalytic denitrification. Herein, we investigated the effects of natural dissolved inorganic and organic matter on catalytic denitrification of contaminated groundwater using a novel Pd-In bimetallic catalyst supported on kaolin derived zeolite (ZK). The developed Pd-In/ZK catalyst showed a highly enhanced performance for denitrification, resulting in a high turnover frequency (18.9 × 10^-3 s-1) and N₂ selectivity (98%). Its application to the NO₃^- contaminated groundwater revealed that humic-like and fulvic-like organic substances potentially inhibited the catalytic NO₃^- reduction and some inorganic ions inhibited the catalytic NO₃^- reduction via different inhibitory mechanisms, i.e. i) the competitive adsorption of Cl- and SO₄ ^2- with NO₃^- and ii) CaCO₃(s)-induced catalyst fouling. The novel findings from this study highlight the potential applicability of ZK as a value-adding support material for catalytic denitrification and emphasize the effect of dissolved organic and inorganic matters in groundwater on the catalytic activity of bimetallic catalysts.