A rapid sample preparation system based on the quick, easy, cheap, effective, rugged, safe (QuEChERS) method was developed for the multi-residue detection of phthalate monoesters (mono-PAEs) in crucian carp by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The samples (1.00 g) underwent extraction with 98% acetonitrile in formic acid, purified using the QuEChERS method, blown down to near dryness under nitrogen gas, reconstituted in acetonitrile:water (1:1, V/V) solution, and filtered through a membrane filter before injection for analysis. The calibration curves for 11 mono-PAEs exhibited good linearity (R² ≥ 0.99903). The limits of detection and quantification were 3.00 and 10.00 μg/kg, respectively. At four spiked concentration levels of 10, 20, 100 and 200 μg/kg, the recoveries of these mono-PAEs ranged from 68.12% to 109.93%, 74.43% to 112.46%, 84.92% to 109.48%, and 82.18% to 108.92%, respectively, with relative standard deviation (RSD) of 1.06% to 8.50%, 0.82% to 4.07%, 0.63% to 2.14%, and 0.79% to 2.66%, respectively. The method exhibited good reproducibility, its recoveries meeting the testing requirements, was simple to operate and sensitive. Therefore, it could meet the need for the trace analysis of multiple mono-PAEs in crucian carp matrices.