PURPOSE: There is limited understanding of the role of postdischarge medical oncology follow-up during care transition periods. Our study describes the care transition patterns and the association between postdischarge medical oncology appointments and downstream health care use at a tertiary academic center. METHODS: We conducted a retrospective cohort study of 25,135 medical oncology admissions between 2018 and 2020 at Yale New Haven Hospital. We examined the association between postdischarge medical oncology appointment timing with 30-day all-cause readmissions and emergency department (ED) visits using multivariable logistic regression models and propensity score–matched analyses. RESULTS: Compared with admissions without appointment within 30 days, admissions with postdischarge medical oncology appointment within 30 days were associated with lower rates of all-cause 30-day readmission (odds ratio [OR] = 0.56, 95% CI, 0.52 to 0.59; P < .001) and ED visit (OR = 0.56, 95% CI, 0.52 to 0.59; P < .001). Admissions with appointment ≤ 14 days were associated with lower rates of 30-day readmission (OR = 0.28, 95% CI, 0.25 to 0.32; P < .001) and ED visit (OR = 0.56, 95% CI, 0.52 to 0.63; P < .001) compared with those with appointment within 15-30 days. Similar patterns in health care use were seen with propensity score matching. Subgroup analyses of cancer types with the most admissions observed similar trends between 30-day readmission and ED visits with appointment timing. CONCLUSION: Timely postdischarge medical oncology appointments were associated with significantly lower likelihood of 30-day readmission and ED visits, suggesting a potential role for postdischarge follow-up as an intervention to decrease health care use.