AIM: To examine the refractive prediction error in high myopic eyes after phacovitrectomy. METHODS: This retrospective comparative case series included 91 eyes (18 high myopic eyes and 73 non-high myopic eyes) of 91 patients who underwent successful phacovitrectomy (phacoemulsification, intraocular lens implantation, and pars plana vitrectomy). The high myopic eyes were defined as the eye with more than 26.0 mm of axial length. The postoperative prediction error of mean error and mean absolute error were evaluated at 4mo postoperatively. Axial length and keratometry measurement were performed preoperatively and 4mo postoperatively using the IOL Master. RESULTS: The refractive outcome after phacovitrectomy showed significantly greater myopic shift in the high myopic eyes [-1.08±0.87 diopters (D)] than that in the non-high myopic eyes (-0.43±0.63 D, P=0.004). Axial length and keratometric value in the high myopic eyes were significantly increased (P=0.043, 0.037 respectively), whereas those in the non-high myopic group were not significantly increased (P=0.135, 0.347 respectively). The change of the axial length in the myopic eye (0.46±0.28 mm) was greater than that in the non-high myopic eye (0.11 ± 0.34 mm; P<0.001). CONCLUSION: High myopic eyes showed more myopic shift than non-high myopic eyes after phacovitrectomy. The cause of myopic shift in high myopic eyes seems to be attributed to actual elongation of the axial length in high myopia.