Background: Arginine vasopressin (AVP) is suggested as an adjunct to norepinephrine in patients with septic shock. Guidelines recommend an AVP dosage up to 0.03 units/min, but 0.04 units/min is commonly used in practice based on initial studies. This study was designed to compare the incidence of hemodynamic response between initial fixed-dosage AVP 0.03 units/min and AVP 0.04 units/min. Methods: This retrospective, multi-hospital health system, cohort study included adult patients with septic shock receiving AVP as an adjunct to catecholamine vasopressors. Patients were excluded if they received an initial dosage other than 0.03 units/min or 0.04 units/min, or AVP was titrated within the first 6 hours of therapy. The primary outcome was hemodynamic response, defined as a mean arterial pressure ≥65 mm Hg and a decrease in catecholamine dosage at 6 hours after AVP initiation. Inverse probability of treatment weighting (IPTW) based on the propensity score for initial AVP dosage receipt was utilized to estimate adjusted exposure effects. Results: Of the 1536 patients included in the observed data, there was a nearly even split between initial AVP dosage of 0.03 units/min (n = 842 [54.8%]) and 0.04 units/min (n = 694 [45.2%]). Observed patients receiving AVP 0.03 units/min were more frequently treated at the main campus academic medical center (96.3% vs. 52.2%, p < 0.01) and in a medical intensive care unit (87.4% vs. 39.8%, p < 0.01). The IPTW analysis included 1379 patients with achievement of baseline covariate balance. There was no evidence for a difference between groups in the incidence of hemodynamic response (0.03 units/min 50.0% vs. 0.04 units/min 53.1%, adjusted relative risk 1.06 [95% CI 0.94, 1.20]). Conclusions: Initial AVP dosing varied by hospital and unit type. Although commonly used, an initial AVP dosage of 0.04 units/min was not associated with a higher incidence of early hemodynamic response to AVP in patients with septic shock.