Myasthenia Gravis is a rare, chronic, acquired autoimmune neuromuscular disorder causing weakness in skeletal muscles. Patients with Myasthenia Gravis face many bio-psychosocial consequences that may require dramatic changes in their lives. The aim of this study was to determine predictors to health promoting behaviors among patients with Myasthenia Gravis using Health Belief Model. A predictive correlational research design was utilized to fulfill the aim of the study. Consecutive sample of convenience consisting of 57 adult male and female patients admitted for 21 months at one of Cairo University Hospitals, Egypt constituted the study sample. Data was collected using the following tools:(a) Demographic and Medical Background Data Form, (b) Glasgow Coma Scale to determine the conscious level of the potential participants, (c) The Adapted Health-Promoting Lifestyle Profile II tool to assess the health-promoting behaviors among the study participants and (d) the Health Belief Model Scale to assess the disease variables that were supposedly act as the predictors to health promoting behaviors among the study participants. Results showed that the majority of participants were female (78.90%), married (66.70%), educated (96.50%) and not working (91.20%), with a mean age of 33.96 ±9.81. Most of the participants have no family history of the disease (96.50%), have generalized Myasthenia Gravis (68.40%), their age at disease onset is between 20 to 40 years old (71.90%) and initial signs and symptoms are ptosis, limbs weakness and dysphagia (49.10 %, 40.40 % and 35.10% respectively). Additionally, more than one third of the study participants achieved low level of total health promoting behaviors. Accordingly, only two health belief model constructs, i.e., self-efficacy and cues to action shown to be predictors to health promoting behaviors. The study recommends that a self-management program should be designed to provide the patients with the necessary tools to improve self-efficacy and enhance management skills.