This study developed a rapid, sensitive, and matrix-free method for the determination of amphetamine (AMP), methamphetamine (MA), codeine (COD), morphine (MOR), and ketamine (KET) using nanostructured silicon surface assisted laser desorption/ionization mass spectrometry (nSi-MS). The nanostructured silicon (nSi) chip used in this study was created by employing the metal-assisted etching process. Drug standard tests were applied to the nSi chip platform to evaluate the nSi-MS performance, including detection sensitivity, limit of detection, linearity, and repeatability. Real urine samples obtained from drug addict detainees were directly applied to the nSi chip for drug analysis. By observing the nSi-MS spectra, the target drug peaks can be identified; and an antibody pull-down assay was performed to confirm the specificity of the detected targets. nSi-MS drug quantification was assayed, yielding comparable results with those from using the GC-MS approach. The advantages of applying nSi-MS to analyze AMP, MA, COD, MOR, and KET in the urine of addicts are simple, extremely small urine volumes (∼10 μL), and a fast analysis procedure (<15 minutes).