We examined the overall and site-specific cancer mortality disparities among first-generation - separately in adults (G1) and children (G1.5) at immigration - and second-generation (G2) immigrants and their countries of origin, using population-based registries in Sweden, encompassing more than 8.5 million individuals aged 20 years or older residing in Sweden since 1990, with follow-up until December 31, 2023. Cox proportional hazard models were fitted, stratified by sex, to estimate hazard ratios and 95% CIs compared with native Swedes. Mortality rates for most cancers transitioned from lower in G1 toward the rate of natives in G2. However, elevated mortality rates were sustained across generations for liver cancer in men and stomach cancer in women. Among G2, mortality rates associated with lymphohematopoietic cancers in men and lung and cervix uteri cancers in women were elevated y 10%, 9%, and 17%, respectively, compared to native Swedes. Country of origin analyses revealed substantial disparities. For instance, G2 women with Nordic parental origin had a 13% higher risk of death from lung cancer, whereas those with non-Western parental origin had a 54% lower risk, as compared to native Swedes. These findings suggest generational and arrival-age dynamics of cancer mortality and highlight target groups for cancer prevention and control among immigrants.