Purpose: Current evidence suggests that phosphoserine aminotransferase 1 (PSAT1) is overexpressed in various tumors. Herein, we investigate the significance of PSAT1 in non-small cell lung cancer (NSCLC) and its correlation with immune infiltration. Methods: The expression profile of PSAT1 in NSCLC patients and related clinical information was obtained from the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA-NSCLC) databases. In silico and experimental validation were conducted to assess the role of PSAT1 in NSCLC. Gene set enrichment analysis (GSEA) was performed to investigate the disparities in biological functions between groups with high and low PSAT1 expression. Additionally, the biological characteristics and immune cell infiltration were compared between these two groups. We also assessed whether PSAT1 expression could predict the sensitivity of NSCLC patients to immunotherapy using the immunophenotype score (IPS) and an anti-PD-L1 immunotherapy cohort (IMvig-or210). Furthermore, the difference in drug sensitivity between PSAT1-high and PSAT1-low expression cell lines was investigated. Results: Analysis of transcriptional expression profiles using TCGA data revealed overexpression of PSAT1 in NSCLC tissues correlated with poor overall survival (OS). GSEA results showed enrichment of DNA recombination and repair, nucleotide biosynthesis, and the P53 signaling pathway in the PSAT1-high group. Experimental validation demonstrated that the knockdown of PSAT1 suppressed cell proliferation, migration, and invasion of NSCLC. Immune cell infiltration analysis revealed an immune-activated tumor microenvironment in the PSAT1-low group. It was also observed that PSAT1-low cell lines were more likely to benefit from immunotherapy and several chemotherapy drugs. Conclusions: PSAT1 has enormous potential for applications in the prediction of NSCLC patient outcomes and provides the foothold for more precise individualized treatment of this patient population.