Background: Genetic mutations are quite common in non-small cell lung cancer (NSCLC), however, their prognostic value remains controversial. Methods: This study explored the mutational landscape of tumor samples from patients with advanced NSCLC by next-generation sequencing (NGS). A total of 101 NSCLC patients in stage III or IV receiving first-line treatment were included. Results: TP53 mutation was the most frequent genetic alteration in NSCLC tumors (68%), followed by EGFR (49%), CDKN2A (12%), LRP1B (9%), and FAT3 (9%) mutations. Among 85 patients with stage IV NSCLC, first-line targeted therapy remarkably prolonged progression-free survival (PFS) of patients compared with first-line chemotherapy (p = 0.0028). Among 65 patients with stage IV NSCLC whose tumors harbored EGFR, ALK, ROS, or BRAF mutations, first-line targeted therapy substantially prolonged the PFS of patients (p = 0.0027). In patients with TP53 mutations who received first-line targeted therapy or chemotherapy, missense mutation was the most common mutation type (36/78), and exon 5 represented the most common mutated site (16/78). Conclusions: TP53 mutation in exon 5 could independently predict poor PFS of patients with stage IV NSCLC after the first- line treatment. Moreover, mutations in TP53 exon 5 and LRP1B were associated with shorter PFS of such patients whether after first-line chemotherapy or targeted therapy, respectively. Thus, these patients should be given immunotherapy or immunochemotherapy.