IMPORTANCE: Because major surgery carries significant risks for older adults with comorbid conditions, shared decision-making is recommended to ensure patients receive care consistent with their goals. However, it is unknown how often shared decision-making is used for these patients. OBJECTIVE: To describe the use of shared decision-making during discussions about major surgery with older adults. DESIGN, SETTING, AND PARTICIPANTS: This study is a secondary analysis of conversations audio recorded during a randomized clinical trial of a question prompt list. Data were collected from June 1, 2016, to November 31, 2018, from 43 surgeons and 446 patients 60 years or older with at least 1 comorbidity at outpatient surgical clinics at 5 academic centers. INTERVENTIONS: Patients received a question prompt list brochure that contained questions they could ask a surgeon. MAIN OUTCOMES AND MEASURES: The 5-domain Observing Patient Involvement in Decision-making (OPTION5) score (range, 0-100, with higher scores indicating greater shared decision-making) was used to measure shared decision-making. RESULTS: A total of 378 surgical consultations were analyzed (mean [SD] patient age, 71.9 [7.2] years; 206 [55%] male; 312 [83%] White). The mean (SD) OPTION5 score was 34.7 (20.6) and was not affected by the intervention. The mean (SD) score in the group receiving the question prompt list was 36.7 (21.2); in the control group, the mean (SD) score was 32.9 (19.9) (effect estimate, 3.80; 95% CI, -0.30 to 8.00; P = .07). Individual surgeon use of shared decision-making varied greatly, with a lowest median score of 10 (IQR, 10-20) to a high of 65 (IQR, 55-80). Lower-performing surgeons had little variation in OPTION5 scores, whereas high-performing surgeons had wide variation. Use of shared decision-making increased when surgeons appeared reluctant to operate (effect estimate, 7.40; 95% CI, 2.60-12.20; P = .003). Although longer conversations were associated with slightly higher OPTION5 scores (effect estimate, 0.69; 95% CI, 0.52-0.88; P < .001), 57% of high-scoring transcripts were 26 minutes long or less. On multivariable analysis, patient age and gender, patient education, surgeon age, and surgeon gender were not significantly associated with OPTION5 scores. CONCLUSIONS AND RELEVANCE: These findings suggest that although shared decision-making is important to support the preferences of older adults considering major surgery, surgeon use of shared decision-making is highly variable. Skillful shared decision-making can be done in less than 30 minutes; however, surgeons who engage in high-scoring shared decision-making are more likely to do so when surgical intervention is less obviously beneficial for the patient. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02623335.