The aim of this study was to investigate prevalence and risk factors associated with spasticity at 3 months after a first-ever stroke in Korean patients. This cohort study included consecutive patients with first-ever stroke who were admitted to 9 participated hospitals in different areas of Korea. The Modified Ashworth Scale (MAS), which defines spasticity as MAS > 1 in any of the examined joints was used to assess patients 3 months after stroke occurrence. The prevalence of spasticity was 7.3% (339 of 4,658 patients), 3 months after stroke onset. Spasticity was more frequent in upper extremity (6.7%) than lower extremity (4.3%). Severity of spasticity was as follows: 63.1%: MAS I, 23.3%: MAS I+, 9.4%: MAS II, 2.6%: MAS III, and 1.4%: MAS IV. Stroke type (hemorrhagic) (p < 0.05) were identified as correlated risk factors. Patients with spasticity scored higher with National Institute of Health Stroke Scale (NIHSS) and lower with modified Rankin Scale (mRS) than non-spastic patients (p < 0.001). This study showed 7.3% prevalence of spasticity in Korean first-ever stroke patients at 3 months, and identified those who carried higher risks of developing spasticity who would particularly benefit from preventive or therapeutic strategies. It would contribute to assessing spasticity in patients with first-ever stroke in Korea.