OBJECTIVE The Decision Regret Scale (DRS) is a valid instrument evaluating the "correctness" of a treatment decision from the patient perspective. The minimal clinically important difference (MCID) is proposed as a threshold for patient-reported outcome measure (PROM) improvement success. The relationship between decision regret and failure to achieve clinical success in adult spinal deformity (ASD) surgeries is not known. The authors sought to examine the relationships between the DRS and outcomes, as measured by the Scoliosis Research Society-22r (SRS-22r), in ASD surgery. METHODS ASD patients with a minimum 2-year follow-up completed the DRS and SRS-22r questionnaires. Records were reviewed for complications and revision surgeries. SRS-22r domain scores were dichotomized as successful or not by MCID values. Patients with DRS scores of 0–20 were defined as having no decision regret. Relationships between DRS and SRS-22r domain scores were explored, as were relationships between DRS and complication/revision surgery. RESULTS A total of 46 patients met inclusion criteria. The average age was 64 years, and the average follow-up was 4.3 years (range 2.0–15.5 years). The mean DRS score was 7.6 with a median score of 0; 15% (7/46) expressed decision regret. Worse SRS-22r pain (p = 0.049), function (p = 0.03), and satisfaction (p = 0.006) were associated with higher DRS scores. Rates of decision regret were not different between those achieving MCID and those who did not (pain, p = 0.1; function, p = 0.1; self-image, p = 0.4; and subscore p = 0.09). There was no difference in the number of patients with decision regret in terms of postoperative complications or patients requiring revision surgery and those who did not. CONCLUSIONS Decision regret after ASD surgeries was uncommon despite complications, reoperations, and failure to achieve MCID changes in SRS-22r domains. Worse SRS-22r pain, function, and satisfaction scores were associated with more decision regret, however.