The purpose of this study was to compare the slouched and upright sitting positions on lumbar joint reposition error (LJRE). Twenty subjects without low back pain were recruited for this study and, using a random number table, were randomly assigned to two groups; the upright sitting position group (UP group) and the slouched sitting position group (SP group). UP group was first asked to sit in an upright position and the SP group to sit in a slouched position as an intervention, and then the LJRE of both groups was measured at the neutral sitting position (lumbar flexion ). The measurement of the LJRE was repeated after one day. The sitting positions were performed for five minutes each and the LJRE was measured using an electronic goniometer. An independent t-test was used to compare the LJRE of both groups after each sitting position and after one day. The results of this study showed that the LJRE after an intervention in the UP group was lower than in the SP group (p<.05) and the LJRE after one day in the UP group was lower than in the SP group (p<.05). The findings of this study indicate that the upright sitting position can be applied to decrease LJRE, compared with the slouched sitting position. These findings also support that the upright sitting position reduces the potential for proprioceptive loss.