IMPORTANCE: There have been substantial improvements in the early detection, treatment, and survival from cancer in the United States, but it is not clear to what extent patients with different types of health insurance have benefitted from these advancements. OBJECTIVE: To examine trends in cancer survival by health insurance status from January 1997 to December 2014. DESIGN, SETTING, AND PARTICIPANTS: California Cancer Registry (a statewide cancer surveillance system) data were used to estimate population-based survival by health insurance status in 3 calendar periods: January 1997 to December 2002, January 2003 to December 2008, and January 2009 to December 2014 with follow-up through 2014. Overall, 1 149 891 patients diagnosed with breast, prostate, colorectal, or lung cancer, or melanoma in California were included in the study. MAIN OUTCOMES AND MEASURES: Five-year all-cause and cancer-specific survival probabilities by insurance category and calendar period for each cancer site and sex; hazard ratios (HRs) and 95% CIs for each insurance category (none, Medicare, other public) compared with private insurance in each calendar period. RESULTS: According to data from 1 149 891 patients diagnosed with breast, prostate, colorectal, or lung cancer, or melanoma gathered from the California Cancer Registry, improvements in survival were almost exclusively limited to patients with private or Medicare insurance. For patients with other public or no insurance, survival was largely unchanged or declined. Relative to privately insured patients, cancer-specific mortality was higher in uninsured patients for all cancers except prostate, and disparities were largest from 2009 to 2014 for breast (HR, 1.72; 95% CI, 1.45-2.03), lung (men: HR, 1.18; 95% CI, 1.06-1.31 and women: HR, 1.32; 95% CI, 1.15-1.50), and colorectal cancer (women: HR, 1.30; 95% CI, 1.05-1.62). Mortality was also higher for patients with other public insurance for all cancers except lung, and disparities were largest from 2009 to 2014 for breast (HR, 1.25; 95% CI, 1.17-1.34), prostate (HR, 1.17; 95% CI, 1.04-1.31), and colorectal cancer (men: HR, 1.16; 95% CI, 1.08-1.23 and women: HR, 1.11; 95% CI, 1.03-1.20). CONCLUSIONS AND RELEVANCE: After accounting for patient and clinical characteristics, survival disparities for men with prostate cancer and women with lung or colorectal cancer increased significantly over time, reflecting a lack of improvement in survival for patients with other public or no insurance. To mitigate these growing disparities, all patients with cancer need access to health insurance that covers all the necessary elements of health care, from prevention and early detection to timely treatment according to clinical guidelines.