This study aimed to evaluate the effects of Khorramabad River water quality on the drip irrigation system and olive fruit quality in the Khorramabad Olive Orchard. Water samples were taken from the Khorramabad River across four seasons—summer, autumn, winter (2024), and spring (2025)—at three locations: the river pumping site, before, and after the irrigation filtration system. Thirty water quality parameters were analyzed, including temperature, salinity, pH, EC, TDS, TH, cations, anions, dissolved oxygen, biochemical oxygen demand (BOD₅), chemical oxygen demand (COD), nitrate, phosphate, and heavy metals (Cd, As, Cr, Pb, Hg, Ni, Al, B, V, Mn). To assess the effect of river water quality on olive fruits, two series of olive samples were collected—table olives (November 2024) and oil-producing olives (December 2024)—and their heavy metal concentrations were measured. The Langelier Saturation Index (LSI) indicated that Khorramabad River water tends to be scaling in summer and highly corrosive in winter. Sodium Adsorption Ratio (SAR) values were below 1 for all seasons, classifying the water as excellent (S1). Heavy metal assessment showed that lead concentrations in olive oil from three cultivars (Mari, Roghni, and Shengeh) exceeded permissible limits, while cadmium and arsenic concentrations in both table and oil olives were below the tolerance thresholds.