Early-onset colorectal cancer (EOCRC), recognized as a distinct subgroup with an increased incidence over the past two decades, characterized by its aggressive nature and potentially unique molecular factors that differentiate it from traditional colorectal cancer (CRC). In this study, we investigated differentially expressed genes in a young-CRC patient using paired-end mRNA-sequencing. Validation of target genes through qRT-PCR highlighted a significant increase in SERPINA3 levels in EOCRC, representing a novel finding. Epithelial expression of SERPINA3 demonstrated a strong association with disease progression, whereas stromal expression showed a negative correlation. Our findings reveal the distinct expression patterns and potential involvement of SERPINA3 in both the initiation and progression of CRC, suggesting that SERPINA3 could serve as a marker for distinguishing early-onset from late-onset cases.