Objectives: Older adults with total knee arthroplasty (TKA) have a limited range of knee joint motion due to pain and stiffness. A roller massager (RM) has recently been suggested to decrease pain and increase joint range of motion (ROM). Therefore, this study aimed to investigate the acute effect of RM intervention on pain and knee joint ROM in older adults with TKA in the second postoperative week. Methods: The participants were 23 patients (76.3±5.4 years) who had undergone TKA for knee OA. The degree of pain during the ROM measurements was measured using the visual analog scale before and immediately after the RM intervention. The RM intervention was performed on the thigh’s lateral, central, and medial parts for three sets of 60 s using an RM. Results: RM intervention could significantly increase knee flexion ROM (p<0.01, d=0.41, ∆change: 4.1±3.2°) and decrease pain during the knee ROM measurements (p<0.01, d=0.53, ∆change: -11.9±21.0). Conclusions: The three sets of 60-s RM intervention significantly increased knee flexion ROM and reduced pain in older adults with TKA in the second postoperative week. These results show that RM intervention is an effective tool for treating stiffness and pain after TKA.