Initial evidence suggests that state-level regulatory mandates for sepsis quality improvement are associated with decreased sepsis mortality. However, sepsis mandates require financial investments on the part of hospitals and may lead to increased spending. We evaluated the effects of the 2013 New York State sepsis regulations on the costs of care for patients hospitalized with sepsis. Retrospective cohort study using state discharge data from the U.S. Healthcare Costs and Utilization Project and a comparative interrupted time series analytic approach. Costs were calculated from admission-level charge data using hospital-specific cost-to-charge ratios. General, short stay, acute care hospitals in New York, and four control states: Florida, Massachusetts, Maryland, and New Jersey. All patients hospitalized with sepsis between January 1, 2011, and September 30, 2015. The 2013 New York mandate that all hospitals develop and implement protocols for sepsis identification and treatment, educate staff, and report performance data to the state. The analysis included 1,026,664 admissions in 520 hospitals. Mean unadjusted costs per hospitalization in New York State were $42,036 ± $60,940 in the pre-regulation period and $39,719 ± $59,063 in the post-regulation period, compared with $34,642 ± $52,403 pre-regulation and $31,414 ± $48,155 post-regulation in control states. In the comparative interrupted time series analysis, the regulations were not associated with a significant difference in risk-adjusted mean cost per hospitalization (p = 0.12) or risk-adjusted mean cost per hospital day (p = 0.44). For example, in the 10th quarter after implementation of the regulations, risk-adjusted mean cost per hospitalization was $3,627 (95% CI, -$681 to $7,934) more than expected in New York State relative to control states. Mandated protocolized sepsis care was not associated with significant changes in hospital costs in patients hospitalized with sepsis in New York State.