Trunk instability is one of main problems in survivors following stroke. We investigated the effects of weight-shift training (WST) on an unstable surface in sitting position on trunk control, proprioception, and balance in individuals with chronic hemiparetic stroke. Eighteen participants with chronic hemiparetic stroke were recruited and were allocated to either WST or control group. The WST group received a weight-shift training program for 30 min and then received a conventional exercise program for 30 min, while the control group received conventional exercise program for 60 min, five times a week for four weeks for both groups. In this randomized control study, we used three outcome measures: trunk reposition error (TRE), Trunk Impairment Scale (TIS), and Timed Up and Go (TUG) test. TRE was measured by each participant’s reposition error to the target angle during his/her active trunk movement. TIS and TUG were examined for trunk control abilities and dynamic balance abilities, respectively. After training, TRE showed significantly greater improvement in the WST group (mean change, 1.67 ± 1.45˚) than the control group (mean change, 0.08 ± 1.05˚). The TIS score was significantly higher in the WST group (mean change, 2.33 ± 1.50) than the control group (mean change, 0.13 ± 0.83). The TUG test also showed a significant improvement in the WST group (mean change, 5.03 ± 1.88 sec) than the control group (mean change, 2.59 ± 1.86 sec). Our findings indicate that weight-shift training is beneficial for improving trunk control and proprioception in patients with chronic hemiparetic stroke.