Heavy metals in water are detrimental to both human health and the environment. This study delineated the assessment of heavy metal contamination using AHP-based HPI and their associated health risk through Monte Carlo simulation. Triplicate samples of ground water were collected from 28 locations in Leh town (Ladakh) for the two seasons, i.e., summer and winter. The study revealed higher concentration of chromium (40–179 µg/L), Cadmium (5–12 µg/L), and Iron (90–2060 µg/L) beyond their permissible guideline values (IS 10500). The seasonal effect on the ground water quality was not pronounced due to cold desert region and the concentration were comparatively higher in summer than winter. AHP-HPI analysis of groundwater using AHP based modified criteria weights demonstrated higher accuracy than the conventional methods of HPI determination. The study revealed that about 96.43% of samples fall under highly polluted category which may be attributed to high concentration of Cr, Cd, Fe and Mn which showed strong Pearson correlation with AHP-HPI and thus, were mostly responsible for deteriorating the groundwater quality of the region. Multi-exposure pathways risk analysis using Monte Carlo simulation revealed that 95th percentile of carcinogenic risk in children (5.54E −03) was about 3 times higher than adults (2.38E-03). The non-carcinogenic risk was evaluated using quantification of Hazard Index (HI) which followed the order of Cr > Mn > Cd > Fe > Ni > Zn. The sensitivity analysis revealed that concentration of metal was major influential factors followed by body weight and exposure duration causing overall health risk.