ImportanceMultimorbidity and postoperative clinical decompensation are common among older surgical patients with cancer, highlighting the importance of primary care to optimize survival. Little is known about the association between primary care use and survivorship among older adults (aged ≥65 years) undergoing cancer surgery.ObjectiveTo examine primary care use among older surgical patients with cancer and its association with mortality.Design, Setting, and ParticipantsIn this retrospective cohort study, data were abstracted from the electronic health record of a single health care system for older adults undergoing cancer surgery between January 1, 2017, and December 31, 2019. There were 3 tiers of stratification: (1) patients who had a primary care practitioner (PCP) (physician, nurse practitioner, or physician assistant) vs no PCP, (2) those who had a PCP and underwent surgery in the same health system (unfragmented care) vs not (fragmented care), and (3) those who had a primary care visit within 90 postoperative days vs not. Data were analyzed between August 2023 and January 2024.ExposurePrimary care use after surgery for colorectal, head and neck, prostate, ovarian, pancreatic, breast, liver, renal cell, non–small cell lung, endometrial, gastric, or esophageal cancer.Main Outcomes and MeasuresPostoperative 90-day mortality was analyzed using inverse propensity weighted Kaplan-Meier curves, with log-rank tests adjusted for propensity scores.ResultsThe study included 2566 older adults (mean [SEM] age, 72.9 [0.1] years; 1321 men [51.5%]). Although 2404 patients (93.7%) had health insurance coverage, 743 (28.9%) had no PCP at the time of surgery. Compared with the PCP group, the no-PCP group had a higher 90-day postoperative mortality rate (2.0% vs 3.6%, respectively; adjusted P = .03). For the 823 patients with unfragmented care, 400 (48.6%) had a primary care visit within 90 postoperative days (median time to visit, 34 days; IQR, 20-57 days). Patients who had a postoperative primary care visit were more likely to be older, have a higher comorbidity burden, have an emergency department visit, and be readmitted. However, they had a significantly lower 90-day postoperative mortality rate than those who did not have a primary care visit (0.3% vs 3.3%, respectively; adjusted P = .001).Conclusions and RelevanceThese findings suggest that follow-up with primary care within 90 days after cancer surgery is associated with improved survivorship among older adults.