We evaluated the presence of "tendon irritation" of flexor pollicis longus (FPL) for cases of distal radius fracture treated with volar plates to prevent FPL tendon rupture. This report details cases of 24 patients. The presence of pain or a sense of incompatibility and subdermal crepitus around the wrist with an active thumb motion were defined as symptoms of FPL tendon irritation. Twelve of 24 patients complained of FPL tendon irritation. The plates were removed in nine of these 12 patients, while tendon injury was found in three cases. The other 12 patients did not complain of FPL tendon irritation. Four of these 12 patients underwent plate removal, and tendon injury was not detected. The results of this study indicate that FPL tendon irritation is likely to appear before tendon rupture. Therefore, FPL tendon rupture might be prevented by plate removal in patients who complained of tendon irritation.