The pheomelanin precursor 5-S-cysteinyldopa (5SCD) exhibits promising potential as a urinary and serum biomarker for melanoma. Nonetheless, it is important to note that 68.8% of early-stage melanoma cases remained undetected when employing 5SCD as a biomarker, underscoring the inadequacy of its efficacy, especially in identifying stage I/II melanoma. In lieu of detecting free 5SCD, the hydrolysis products of pheomelanin, namely, 4-amino-3-hydroxyphenylalanine (4-AHP) and 3-amino-4-hydroxyphenylalanine (3-AHP) offer the prospect of achieving heightened sensitivity and broader scope in early-stage melanoma diagnosis through direct chemical processes. This study introduces an innovative gas chromatography-mass spectrometry (GC-MS) methodology to identify early-stage melanoma by comparing the concentrations of AHPs across 80 stage I/II melanoma patients against 32 healthy controls. The approach demonstrated linear response within the 0.5-20 μg/mL range for reference AHPs detection. The urine levels of AHPs were 1.3 ± 0.5 μg/mL in the control/volunteer group (n = 32), 8.1 ± 1.6 μg/mL in stage I and II melanoma patients (n = 28), and 6.3 ± 1.9 μg/mL in stage II melanoma patients (n = 52). The findings unequivocally underscore the diagnostic promise of AHPs as a robust tool for early-stage melanoma assessment in laboratory medicine.