A sensitive and direct method for quantification of N-nitrosodiethanolamine (NDELA) in ethanolamine has been developed. The sample was dissolved in water and directly injected to high performance liquid chromatography with mass spectrometry to quantify NDELA. The eluent was transferred to mass spectrometer and ionized by heated electrospray positive ionization. The analyte was quantified in parts per billion level by using multiple reaction monitoring (MRM) mode. The MRM transition was m/z 135.0 to 74.1 and confirmed by m/z 104.0. To avoid ion suppression and better sensitivity for quantification, cation exchange column was used. A linearity coefficient of R2 >0.995 was observed in calibration over a wide range of concentration 1 ppb to 10 ppb of NDELA. The method was validated by linearity, accuracy and precision studies. The results show that recoveries were in between 97% to 106%.