This study aimed to determine the immediate effects of somatosensory stimulation on hand function in patients with poststroke hemiparesis. Eleven patients with poststroke hemiparesis participated in this study. Four types (no stimulation, vibration, and light and rough touches) of somatosensory stimulation were performed randomly for 4 days applying only one type of somatosensory stimulation each day. The box and block test (BBT), the Jebsen–Taylor hand function test (JTHFT), hand grip strength (HGS), and movement distance and peak velocity of the wrist joint during a forward-reaching task were measured. The BBT and JTHFT scores for no stimulation [BBT: median (interquartile range), 0.00 (−1.00 to 1.00) and JTHFT: 2.57 (−0.47 to 4.92)] were significantly different from those for vibration [BBT: 3.00 (2.00–5.00) and JTHFT: −16.02 (−23.06 to −4.31)], light touch [BBT: 3.00 (1.00–4.00) and JTHFT: −5.00 (−21.20 to −0.94)], and rough touch [BBT: 2.00 (1.00–4.00) and JTHFT: −6.19 (−18.22 to −3.70)]. The JTHFT score was significantly higher for vibration than that for rough touch (P<0.05). The increase in HGS was significantly greater for light touch than that for no stimulation (P<0.05) and for vibration than that for light touch (P<0.05). There were significant differences for the sagittal and coronal planes in movement distance and for the sagittal and horizontal planes in peak velocity during the forward-reaching task (P<0.05). The findings suggest that somatosensory stimulation may be advantageous to improve the hand function of patients with poststroke hemiparesis, with more favorable effects observed in vibration stimulation.