The main aim of this research was to provide a complete and new ultraviolet (UV) analysis of acetylsalicylic acid, a non-steroidal drug, in acetonitrile as a solvent. It is a low-cost method which is accurate, precise, easy to apply, and needs low reagent consumption. Using this method, we can precisely find the amount of pure acetylsalicylic acid from various pharmaceuticals in any specialized laboratories. A statistical validation process was successfully applied. The linearity of the method, system precision, method precision, method robustness, and method accuracy were studied and successfully determined. To evaluate the linearity of the method and exactly quantify pure acid acetylsalicylic acid from two pharmaceuticals by the proposed method, the absorption spectrum was plotted for a standard solution of 16.83 µg/mL in acetonitrile p.a. as a pure spectral solvent. The maximum absorption wavelength was found to be λ = 213 nm. The ultraviolet spectrophotometric method was linear over the entire concentration range between 1.20 µg/mL and 16.00 µg/mL, and the linear regression value was R² = 0.999. Acetylsalicylic acid pure calculated content was found to be 497.46 mg for the first pharmaceutical and 494,67 mg for the second product. These amounts were very close to the officially stated content of 500 mg, with very low average percentage deviations from this official content, (+) 0.51 % and (+) 1.06 %, respectively. The calculated average percentage deviations were below the maximum percentage limit (± 5%) stated by the European and International Pharmacopoeias Rules. This method can be easily applied for the Technical Quality Control of pharmaceutical products containing acetylsalicylic acid as an active substance.