Environmental contamination by xenobiotics is a worldwide phenomenon being mainly caused by human activities and urbanization. The release of harmful substances leaves short and long term effects in the environment. This study assessed the acute toxicological effects of different concentrations of chloroxylenol (PCMX), an active ingredient in most liquid cleaning products, on the whirligig beetle Orectogyrus alluaudi Regimbart, 1889. This was done with the aim of determining the potential lethal effects of the chemical on this aquatic organism. The beetle’s behaviour and swimming pattern were both altered by PCMX before mortality occurred. The 24-h, 48-h, 72-h, and 96-h calculated LC50 values were 21.587, 16.744, 11.638 and 7.819 mg/L, respectively. The mortality of the test organisms increased with increased concentration and extended exposure duration. Thus giving an indication that the toxicity of PCMX to the beetles was time and concentration-dependent. The altered behaviour and swimming pattern in the beetles could be ascribed to physiological responses and disturbances in their nervous coordination due to exposure to PCMX.