Purpose The Korean population is rapidly aging, and the cancer burden is expected to change significantly. This study aimed to generate projections of incidence and mortality of major cancers among men in Korea until 2034, with a special focus on prostate cancer. Materials and Methods Cancer incidence data from 1999 to 2016 were obtained from the Korea National Cancer Incidence Database. Mortality data were obtained from Statistics Korea. The most common cancers among Korean men (stomach, colorectum, liver, lung and prostate) were analyzed. To predict the future trends of these cancers, the age-period-cohort method was conducted and extrapolated up to 2034. Results In Korean men, prostate cancer was the fourth most commonly diagnosed cancer in 2016. Based on newly diagnosed cases, the leading cancer site in the year 2034 is expected to be the lung, and the prostate is expected to be the second most frequently diagnosed cancer among Korean men. Age-standardized incidence rates of the most common cancers in men, except prostate cancer, are expected to decrease until 2034. Lung cancer is projected to remain the most common cause of cancer-related mortality until 2034, and the highest estimated change in cancer deaths is expected to be for prostate cancer. Conclusions In Korea, the incidence and mortality of prostate cancer is expected to increase markedly in the period up to 2034, particularly in older men. Concerted efforts in screening, diagnosis, and treatment strategies should be considered by healthcare planners and providers.