Background Numerous studies indicated that workers in the health sector suffer from work stress, hassles, and mental health problems associated with COVID-19, which negatively affect the completion of their job tasks. These studies pointed out the need to search for mechanisms that enable workers to cope with job stress effectively. Objectives This study investigated psychological flow, mental immunity, and job performance levels among the mental health workforce in Saudi Arabia. It also tried to reveal the psychological flow (PF) and mental immunity (MI) predictability of job performance (JP). Method A correlational survey design was employed. The study sample consisted of 120 mental health care practitioners (therapists, psychologists, counselors)who lived in Saudi Arabia. Sixty-four were men, 56 were women, and their ages ranged between 27 and 48 (36.32±6.43). The researchers developed three measurements of psychological flow, mental immunity, and job performance. After testing their validity and reliability, these measures were applied to the study participants. Results The results found median levels of psychological flow, mental immunity, and job performance among mental health care practitioners. Also, the results revealed that psychological flow and mental immunity were statistically significant predictors of job performance. The psychological flow variable contributed (38.70%) and mental immunity (54.80%) to the variance in job performance of mental health care practitioners.