The quantification of pesticides in complex environmental matrices such as tree leaf litter requires efficient analytical methods to determine reliable concentrations at environmental low levels. To this aim, a method was developed for the determination of 15 pesticides in leaf litter using QuEChERS followed by ultra-high performance liquid chromatography coupled to tandem mass spectrometry. This method was validated and its analytical uncertainties were determined according to French standards. Linearity and limits of quantification were statistically tested and the efficiency, repeatability and expanded uncertainties were evaluated for each compound. The optimized QuEChERS method is reliable, specific and sensitive.