Anaplastic lymphoma kinase (ALK) plays important roles in tumorigenesis and is involved in tumor immunogenicity through various pathways. Here, we conducted a comprehensive bioinformatic and clinical analysis on the characteristics of pan-cancer ALK mutation and its association with tumor immunity and the efficacy of immune checkpoint blockade. In 2930 patients with 11 tumor types treated with immune checkpoint inhibitors, the mutation of ALK indicated favorable overall survival (hazard ratio = 0.69; 95% confidence interval, 0.57–0.83; p < 0.001). We further developed and validated a nomogram to estimate the 12-month and 24-month survival probabilities after the initiation of immunotherapy. Moreover, multi-omics analysis on both intrinsic and extrinsic immune landscapes revealed that the mutation of ALK could enrich infiltration of immune cells, enhance tumor immunogenicity, and improve immune responses. In conclusion, ALK mutation is associated with promoted cancer immunity and can be treated as a biomarker for favorable outcomes in pan-cancer immune checkpoint blockade. These results have implications for treatment decision-making and developing immunotherapy for personalized care.