Purpose This study aimed to investigate the effects of manual assist training using cough combined with trunk stabilization exercise on muscular activity and proprioception in a hemiplegic patient with subacute stroke. Methods A 43-year-old hemiplegic patient with a cerebral infarction performed the intervention for 45 minutes three times per week for 4 weeks from March 11 to April 5, 2024. The trunk muscle activity and the position sense of the hemiplegic patient were evaluated before and after the intervention. and trunk stability was evaluated using the trunk impairment scale. Results The activities of the internal oblique, external oblique, rectus abdominis, and multifidus muscles increased from 34.25, 38.14, 43.05, and 40.74% pre-intervention to 47.53, 56.31, 64.17, and 52.32% post-intervention, respectively. The sense of position of the trunk decreased from 11.7˚ before the intervention to 6.5˚ after the intervention. The trunk impairment scale score increased from 13 points pre-intervention to 19 points post-intervention. Conclusion The manual assist training combined with trunk stabilization exercise improved trunk muscle activity, proprioceptive sense, and body control in a patient with subacute hemiplegia. We hope that these findings will contribute to interventions and basic data of the early rehabilitation of patients with stroke.