Objective: The 14-item Treatment Satisfaction Questionnaire for Medication Version I (TSQM) is a reliable and valid instrument to assess patients' satisfaction with medication, providing scores on four scales—side effects, effectiveness, convenience and global satisfaction. In naturalistic studies, using the TSQM with the side effects domain has a potential to interfere with routine medical care. In this study, an interactive voice response system (IVRS)-administered abbreviated 9-item TSQM without the five items of the side effects domain (TSQM-9) was psychometrically evaluated among patients taking antihypertensive medication. Methods: A total of 396 subjects who self-reported taking a prescribed antihypertensive medication were recruited from an online panel. The subjects were asked to complete the TSQM-9 at the start of the study, along with the modified Morisky scale, and then again within 7 to 14 days. Psychometric analyses including confirmatory factor analysis (CFA), Cronbach's alpha and intraclass correlation coefficients were conducted. Results: There was evidence of construct validity of the TSQM-9 based on the CFA findings of the observed data fitting the Decision Balance Model of Treatment Satisfaction even without the side effects domain (Non-normed Fit Index=0.9791; Bentler's Comparative Fit Index=0.9860). TSQM-9 domains had good internal consistency as evident from Cronbach's alpha values of 0.84 and greater. TSQM-9 domains also demonstrated good test-retest reliability with high intraclass correlation coefficients exceeding 0.70. As expected, the TSQM-9 domains were able to differentiate between individuals who were high compliers with medication use and those that were low compliers, with a moderate-to-high effect size (Cohen's d ranging from 0.6 to 0.8). There was evidence of convergent validity with significant correlations with the medication adherence scale. Conclusion: The IVRS-administered TSQM-9 was found to be a reliable and valid measure to assess treatment satisfaction in naturalistic study designs, in which there is potential for the TSQM's side effects domain to interfere with routine clinical care.