Rationale and Objective Recent initiatives aim to improve patient satisfaction and autonomy by increasing the use of peritoneal dialysis (PD) in the United States. However, limited knowledge is available about the costs of different dialysis modalities, particularly those incurred by private insurers. In this study, we compared the costs of injectable dialysis drugs (and their oral equivalents) paid by insurers between privately insured patients receiving hemodialysis and PD. Study Design A retrospective cohort study. Setting and Participants From a private insurance claims database, we identified patients who started receiving PD or in-center hemodialysis between January 1, 2017, and December 31, 2020. Exposure Patients started receiving PD. Outcomes Average annual injectable drug and aggregate expenditures and expenditure subcategories. Analytical Approach Patients who started receiving PD were propensity matched to similar patients who started receiving hemodialysis based on the year of dialysis initiation, patient demographics, health, geography, and comorbidities. Cost ratios (CRs) were estimated from generalized linear models. Results We matched 284 privately insured patients who started receiving PD 1:1 with patients started receiving in-center hemodialysis. The average annual injectable drug expenditures for hemodialysis were 2-fold higher (CR: 1.99; 95% CI, 1.62-2.44) than that for PD. Compared those receiving PD, patients receiving hemodialysis incurred significantly lower nondrug dialysis-related expenditures (0.85; 95% CI, 0.76-0.94). The average annual expenditures for non–dialysis-dependent outpatient services were significantly higher among patients who underwent in-center hemodialysis (CR: 1.44; 95% CI, 1.10-1.90). Although aggregate and inpatient hospitalization expenditures were higher for in-center hemodialysis, these differences did not reach statistical significance. Limitations Small sample sizes may have restricted our ability to identify differences in some cost categories. Conclusions Compared with privately insured patients who started receiving PD, patients starting in-center hemodialysis incurred higher expenditures for injectable dialysis drugs, whereas differences in other expenditure categories varied. Recent increases in the use of PD may lead to reductions in injectable dialysis drug costs among privately insured patients. Plain Language Summary Recent initiatives aim to improve patient satisfaction and autonomy by increasing the use of peritoneal dialysis (PD) in the United States. However, limited knowledge is available about the costs of different dialysis modalities, particularly those incurred by private insurers. In this study, we compared the costs of injectable dialysis drugs (and their oral equivalents) provided by insurers between privately insured patients receiving hemodialysis and PD. We found that the average annual injectable drug expenditures for hemodialysis were 2.0-fold higher compared with those for PD. These findings suggest that the recent increase in the use of PD may lead to reductions in injectable dialysis drug costs among privately insured patients.