Lack of social trust in the physician–patient relationship will disrupt health. Since social trust has not been sufficiently studied in patients' companions, this study investigates and compares social trust and its dimensions in companions of patients discharged against medical advice with total patients’ companions in the emergency room. In this cross-sectional descriptive-comparative study, 385 patients’ companions were enrolled. This study was done by a questionnaire with five subscales: honesty, frankness, cooperative tendency, confidence, and trust. Data were analyzed using descriptive statistics and analytical statistics methods. In this study, there was no significant difference between the mean score of social trust between companions of patients discharged against medical advice (61.11 ± 9.01) and patients discharged after treatment (62.27 ± 6.97). There was a significant relationship between the mean score of the 2 groups only in the frankness domain ( P-value = .001). The level of social trust in the patients’ companions was moderate in both groups. Companions of discharged patients after completing the treatment process are more explicit than the companions of patients discharged against medical advice.