This study was undertaken to address the need for an improved analytical method to detect and quantify hindered phenolic antioxidant additives in Navy mobility fuels that overcomes the limitations of currently available methods. It was demonstrated that hindered phenols in fuels can be accurately quantified using capillary gas chromatographymass spectrometry with selected ion monitoring (GCMS/SIM) of mass fragments unique to each analyte. Using this approach, three methods were developed for the analysis of antioxidants in fuels: (1) a single-column GCMS/SIM method that, because of co-elution of fuel constituents, is only suitable for quantifying tri-tert-butylphenol, (2) a two-column heart-cutting method that overcomes the problem of co-eluting fuel components but requires modification of the instrument, and (3) a GCMS/MS method that does not require modification of the instrument. The heart-cutting method was developed as a practical method for the routine determination of each of the five hindered phenolic antioxidants in any type of fuel, with a method quantitation limit (MQL) of 0.5 mg/L, with minimal interference from fuel. The GCMS/MS method provides a lower MQL of 0.05 mg/L. Both methods offer a significant advantage over traditional high-performance liquid chromatography with electrochemical detection (HPLCECD) methods, which are more labor-intensive and not capable of separating each of the individual phenolic antioxidants.