Background Penetrating keratoplasty (PK) is the dominant technique for visual restoration of corneal blindness worldwide. Corneal graft rejection and refractive errors are common postoperative issues of it, but correlation between these complications was seldom reported. To the author’s knowledge, this is the first reported case describing hyperopic change following post-penetrating keratoplasty graft rejection.Case presentation A 15-year-old female undergoing PK for advanced keratoconus in the left eye. Postoperatively, the graft was clear and her corrected distance visual acuity (CDVA) improved to 20/20. Corneal topography revealed anterior chamber depth (ACD) of 5.87 mm and keratometry readings of 42.4/46.1 diopters (D). However, decreasing visual acuity to counting fingers was noted after twelve months. Slit-lamp biomicroscopic examination showed stromal edema and mutton-fat keratic precipitates infiltration. Corneal graft rejection was diagnosed and CDVA resumed to 20/20 within one month after intensive topical and high-dose systemic steroid administration. Four years later, corneal topography revealed an ACD of 2.98 mm and keratometry readings of 42.4/45.1 D with spherical equivalence of + 1.25 D. Clinically and topographically, the corneal graft demonstrated a process of flattening before and after the episode of graft rejection.Conclusions Graft rejection may cause hyperopic shift in patients with keratoconus after PK.