In this work, four non-steroidal anti-inflammatory pharmaceutical products in surface water wereanalyzed by UPLC-MS/MS. Non-steroidal anti-inflammatory pharmaceutical products in surface water were pre-concentrated on a mix-mode cation exchange cartridge. The analytes were then separated on the BEH column utilizing a gradient of methanol and water containing ammonium acetate. The analytes were detected by multi-reaction monitoring mode in tandem mass spectrometry employing negative electrospray ionization. As a result, the repeatability of the retention times and peak areas were below 0.13% and 3.42%, respectively. The method’s detection limit was achieved from 0.021 µg/L to 0.192 µg/L. Recoveries were from 78 to 110% and fell in the acceptable range according to AOAC. Finally, the developed method was applied to analyze these compounds in the surface water. The analyzed results showed that only ibuprofen and diclofenac were detected in the surface water collected from Hanoi.