The purpose of this descriptive study was to evaluate the shared decision making of family caregivers of patients with psychosis in Khunyuam hospital, Khunyuam district, Mae Hong Son province. A study population was selected from family caregivers and 83 cases were included as a sample. Data was collected by the interviewer, and the interview consisted of two parts. Part 1 consisted of population characteristics and treatment information, and Part 2 was an evaluation form about the shared decision making of family caregivers of patients with psychosis by translation and adaptation from the dyadic OPTION Scale. The content validity was based on the Index of Item-Objective Congruence (IOC) and were questions scoring more than 0.67. The reliability obtained by Cronbach’s alpha coefficient was 0.88. Data were analyzed using descriptive statistics including: frequency, percentage, average and standard deviation. The findings showed that the samples of female gender were similar to male most (31.3%) who were from the age of 41 to 50 years, most of them were Buddhists (79.5%) and married (84.3%), and most of them graduated from primary school (39.8%). In addition, about 50% were farmers, the average annual household income was less than 50,000 baht (43.4 %), the relationship between family caregivers and psychiatric patients was mostly the spouse (37.3%), and the number of families with four members accounted for 31.3%. Family caregivers who brought patients into treatment with the goal of a follow up rather than treating patients were 56.6% and 43.4%, respectively, and those who visited with a general practitioner were 63.9%. The family caregivers who brought the patient to treatment more than once was 88.0%, and family caregivers caring for the patient for more than five years accounted for 41.0%. The results of the levels of shared decision making of family caregivers showed that most family caregivers "agree" at more than 60.0%. In regard to the statements, “Different sources of information (e.g. leaflets, websites, contact with other people) to help make the decision were offered” and “The advantages, disadvantages and possible outcomes of options were discussed,” family caregivers wrote "agree" to 51.9% and 59.0%, respectively. Gender and family income having a level of shared decision making were not different. Family caregivers older than 50 years had a level of shared decision making lower than those younger than 50 years. Those with a higher education level had a level of shared decision making higher than those with a lower education level. Husband-wife group family caregivers paid attention to shared decision making more than the other groups. The symptom treatment group had a level of shared decision making higher than the follow-up group. The general practitioners group had a level of shared decision making lower than the psychiatrist group and nurse practitioners practicing mental health clinics group. The care of patients with psychosis of more than five years had a level of shared decision making lower than the care of patients with psychosis with less than five years. This study clearly shows that family caregivers are involved in shared decision making and recognize the importance of the process involved in shared decision making. However, there should be further studies on the development of clinical outcomes by the shared decision making process and determining appropriate policies in the process of shared decision making of the family caregivers of patients with psychosis