An analytical method based on solid phase extraction has been developed and validated for analysis of montelukast in human plasma. Metaxalone was used as an internal standard for montelukast. A HyPURITY Advance C18 column provided chromatographic separation of analytes followed by detection with mass spectrometry. The method involves simple isocratic chromatographic conditions and mass spectrometric detection in the positive ionization mode using an API-4000 system. The proposed method has been validated with linear range of 5–800 ng/mL for montelukast. The intra-run and inter-run precision values are within 4.04% and 9.44% respectively for montelukast at lower limit of quantification level. The overall recovery for montelukast and metaxalone was 70.40% and 94.21% respectively. This validated method was used successfully for analysis of plasma samples from a bioequivalence study.