Background and objective: Patient's adherence is an important factor affecting the successful maintenance of treatment, slow progression of the disease; reduce costs of health care especially in the presence of multiple chronic conditions as rheumatic disorders. While, medication non-adherence is a significant problem leads to increased mortality and morbidity. So, identification of the factors affecting non-adherence to medication regimens is beneficial for healthcare providers to improve patient's health condition. The aim of the study was to determine factors affecting medication adherence among sample of Egyptian patients with rheumatic disorders.Methods: Design: An exploratory descriptive research design. Subjects: Purposive sampling of patients with history of rheumatic disorders. Setting: The study was carried out in rheumatology department and medical wards at Al-Kaser Al-Aini hospital. Tool: Patient Preliminary Informational Variables, Morisky Medication Adherence Scale 8-Items and Factors affecting drug adherence checklist were used to collect pertinent data.Results: The study showed 59.2% of study group had low adherence, followed by medium adherence and high adherence (28%, 12.7%) to prescribed medications respectively. Findings also; revealed that the highest percent of these factors that may combine to render patients to be less able to adhere to prescribed medication ranked as complexity of medication regimen; chronic conditions, restricted formularies, changing medications covered on formularies; fear of possible adverse effects, fear of dependence; lack of continuity of care, treatment interferes with lifestyle or requires significant behavioral changes; patient information materials written at too high literacy level; severity of symptoms; lack of knowledge on adherence and the effective interventions for improving it; as well the medication cost; long wait times; burdensome schedule; poor access or missed appointments; actual or perceived unpleasant side effects; duration of therapy; medication negative effect on liver and kidney; in addition, psychosocial stress, anxiety and anger.Conclusions: Due to the diversity of causes of non-adherence, the health care professionals must understand factors affecting medication adherence when dealing with problems of medication adherence especially with chronic conditions as rheumatic disorders. Recommendation: Interventions for overcoming factors affecting adherence must become a central component of efforts to improve patients' health worldwide. This could be done by proper determination for factors affecting medication adherence, also to consider patient condition individually and modify the treatment approach accordingly.