Immune checkpoint inhibitors open a new door for tumor immunotherapy, but it should not be ignored that some tumor patients are still insensitive to this kind of therapy. The purpose of this study is to analyze the prognostic value of STK11 mutations in metastatic cancer patients treated with ICIs. Information regarding somatic gene mutations of STK11 and patients’ survival time in advanced cancer patients receiving ICIs treatment was downloaded from the cbioportal database. The prognostic value of STK11 gene mutation was analyzed by Log-rank test and multivariate Cox proportional hazards regression analysis. The somatic mutation frequencies of STK11 among all patients were 6.14%, and STK11 gene mutations were mainly distributed in patients with non-small cell lung cancer. The results showed STK11 gene mutation status was associated with shorter survival time, the hazard ratio is1.746 (P <0.0001). The somatic mutations of STK11 were also associated with shorter overall survival in NSCLC patients (P = 0.017). Multivariate Cox proportional hazards regression analysis showed STK11 gene mutation was significantly associated with overall survival (HR= 1.567, 95%CI: 1.209-2.029, P= 0.001). The results of this study suggested that STK11 gene mutation could be used as a negative prognostic marker in metastatic cancer patients receiving ICIs treatment.