This study sought to assess the psychometric properties of the 9-item Shared Decision-Making Questionnaire (SDM-Q-9) in patients with resected, non-metastatic cancer and eligible for adjuvant chemotherapy. A total of 568 patients were recruited from a multi-institutional, prospective, transversal study. Patients answered the SDM-Q-9 after visiting their medical oncologist who, in turn, completed the SDM-Q-Physician version. Reliability, factorial structures [exploratory factor analysis (EFA), confirmatory factor analysis (CFA)], and convergent validity of the SDM-Q-9 scores were explored. SDM-Q-9 showed a clear factorial structure, compatible with a strong and replicable general factor and a secondary group factor, in patients with resected, non-metastatic cancer. Total sum scores derived from the general factor showed good reliability in terms of omega coefficient: .90. The association between patient and physician perception of SDM was weak and failed to reach statistical significance. Males and patients over 60 years of age displayed the greatest satisfaction with SDM. SDM-Q-9 can aid in evaluating SDM from the cancer patients' perspective. SDM-Q-9 is helpful in studies examining patient perspectives of SDM and as an indicator of the degree of quality and satisfaction with health care and patient-physician relationship.