Objective: To investigate and analyse the clinical and immunological features of patients with myositis complicated with thromboembolism. Methods: We identified a cohort of 390 myositis patients diagnosed with myositis admitted to People’s Hospital of Peking University from 2003 to 2019. The patients were retrospectively enrolled in this investigation. According to the outcome of the color Doppler ultrasound, CT pulmonary angiography, pulmonary ventilation and perfusion scan patients were divided into myositis with and without thromboembolism group. Demographic, clinical (heliotrope rash, Gottron’s sign/papules, periungual erythema, skin ulceration, subcutaneous calcinosis, Mechanic’s hands, myalgia, interstitial lung disease, pulmonary arterial hypertension), laboratory, immunological [anti-autoantibodies including melanoma differentiation associated gene 5 (anti-MDA5), anti-Mi-2, anti-transcription intermediary factor-1γ (anti-TIF-1γ, anti-nuclear matrix protein 2 (anti-NXP2), anti-small ubiquitin-like modifier activating enzyme (anti-SAE), anti-synthetase], imaging and therapeutic status data of the patients at the diagnosis of myositis with and without thromboembolism were collected and the differences in these data were analyzed. Logistic regressive analysis was used to identify the risk factors of thromboembolism. Results: In the retrospective study, 390 myositis patients were investigated. The mean age of onset was (49.6±13.4) years, male to female ratio was 0.31:1. Thromboembolism was identified in 4.62% (18/390) of the myositis patients, which was lower than the published reports. Out of 18 patients with thromboembolism, 55.6% (10/18) of them were deep venous thrombosis, followed by cerebral infarction (22.2%, 4/18), pulmonary embolism (11.1%, 2/18), renal artery embolism (5.6%, 1/18) and embolism of upper extremity (5.6%, 1/18). Fifty percent of thromboembolism events occurred 6 months after the diagnosis of myositis, 38.9% of thromboembolism events occurred 6 months within the diagnosis of myositis, 11.1% of thromboembolism events occurred 6 months before the diagnosis of myositis. As compared with the myositis patients without thromboembolism, the myositis patients complicated with thromboembolism were older [(58.3±11.7) years vs. (49.3±13.4) years, P=0.006]. C-reaction protein (CRP) (12.2 mg/L vs. 4.1 mg/L, P<0.001), ferritin (20 085.5 μg/L vs. 216.6 μg/L, P<0.001) and D-dimer (529.0 μg/L vs. 268.0 μg/L, P=0.002) were significantly higher in thromboembolism group. Diabetes (44.4% vs. 16.4%, P=0.006), coronary heart disease (22.2% vs. 3.0%, P=0.003) and surgery (16.7% vs. 3.5%, P=0.032) were observed more common in thromboembolism group than those without thromboembolism. Activated partial thromboplastin time (APTT) (26.9 s vs. 28.7 s, P=0.049) and albumin (32.4 g/L vs. 36.5 g/L, P=0.002) was lower in thromboembolism group. The risk factors of thromboembolism in the myositis patients were low level of albumin (OR=0.831, 95%CI: 0.736-0.939, P=0.003), diabetes (OR=4.468, 95%CI: 1.382-14.448, P=0.012), and coronary heart disease (OR=22.079, 95%CI: 3.589-135.837, P=0.001) were independent significant risk factors for thromboembolism in the patients with myositis. There was no significant difference in clinical manifestations, myositis-specific antibodies or myositis-associated antibodies between the two groups. Conclusion: Thromboembolism is a complication of myositis. Lower levels of albumin, diabetes, and coronary heart disease might be risk factors of thromboembolism in myositis patients.