Health problems caused by high arsenic concentrations (over 200 μg/L) in groundwater sources in the Pannonian Basin (Hungary, Romania, Croatia, Serbia) have become a major concern for researchers and environmental experts. This paper evaluates the effect of the preoxidation (with hypochlorite)/coagulation process (with commercially available coagulant FeCl3) on the removal efficiency of arsenic (with an initial concentration of 235 ± 0,6 μg/L) from a groundwater source for a small rural community in western Romania, at laboratory scale. The results of this experimental study showed that, through the preoxidation/coagulation process, the arsenic concentration is removed up to 94% from the groundwater used. Since coagulation and flocculation are simple and commonly applied in drinking water treatment plants in most countries of the Pannonian Basin, this work aims to contribute to long-term improvement of drinking water in this geographical area, with groundwater sources naturally contaminated with arsenic.