<p>A class of novel synthetic opioids, nitazenes, have infiltrated the illicit drug market worldwide. Their high potency leading to overdose and fatality is a public health concern. Xylazine is a non-opiate sedative typically used for veterinary applications. The drug has recently appeared as an adulterant in the informal drug market, particularly within opioid drugs such as fentanyl and heroin. Determining the extent of use of these drugs is challenging due to low levels consumed. Wastewater analysis has been applied to monitor novel psychoactive substance use at a population level. This study presents the validation of a sensitive analytical method for the detection and quantification of trace levels of nitazenes and xylazine in wastewater. A solid phase extraction method was employed, yielding a concentration factor of 1000-fold. The method was applied to wastewater samples collected in Australia. Five different nitazenes were found near the limit of detection and quantitation levels, with detection frequencies ranging from 3 to 6% of all samples analysed. Xylazine was detected at a higher detection frequency (26% of all samples analysed). The method presented in this study could be used as an early warning system to track the use of xylazine and nitazenes internationally.</p>