Nonmedical use of benzodiazepines and their analogues is increasing, with supplies often sourced from inner circles or open internet sources and crypto markets where products are frequently mislabeled. There fore, fast, reliable, and simple analytical methods are crucial for accurate identification and quantification. This study aimed to develop and validate a quantitative Nuclear Magnetic Resonance (qNMR) method using a benchtop NMR(1H, 60 MHz)instrument and 3-(trimethylsilyl)propionic-2,2,3,3-d4 acid sodium salt as internal calibrant for the analysis of diazepam. The method proved to be specific and selective, with minor interferences caused by a few cutting agents and structurally related compounds. The precision and accuracy results were within the requirements of the United Nations Office on Drugs and Crime guidelines, yielding an LOD of 0.14 mg/mL, an LOQ of 0.46 mg/mL, and a recovery rate of 95%. The testing batch analysis of 100 street tablets resulted diazepam contents ranging from 0.52 mg to 26.20 mg per tablet. Although the average diazepam content in tablets collected between 2002 and 2023 varied, the limited number of samples per year prevented a reliable assessment of temporal trends. However, the variation highlights the need for continuous and comprehensive monitoring to inform and educate individuals who access these substances and to improve harm reduction services. This study confirmed the high efficacy and suitability of benchtop qNMR for analyzing diazepam content in street samples. Future work should expand the sample size and adapt the method to include other benzodiazepine analogues.