AIM: To report the postoperative axial length (AL) changes in rhegmatogenous retinal detachment combined with choroidal detachment (RRD-CD) patients. METHODS: The medical records of 97 consecutive patients from January 2015 to December 2018 were reviewed. Patients included were divided into RRD-CD and RRD only groups. All patients had received AL measurements before pars plana vitrectomy (PPV) and before silicone oil removal (SOR). The changes in AL of the two groups were compared. In addition, the potential factors related to AL changes were analyzed. RESULTS: AL elongation after PPV was 1.01 mm [interquartile range (IQR): 0.37, 1.79; P=0.02] in the RRD-CD group, which was greater than in RRD only group (0.15 mm, IQR: 0.04, 0.41; P<0.001). AL increased 0.06 mm per 1 mm Hg intraocular pressure changes in the RRD-CD group (R-2=0.11, P=0.03). RRD-CD patient was 11.42 times (3.54-46.80) more likely to experience post-PPV AL elongation of more than 1 mm [P<0.001, Akaike information criterion (AIC)=92.33, area under the curve (AUC)=0.839]. CONCLUSION: RRD-CD patients are very likely to have a postoperative elongation of AL. The primary intraoclular lens implantation using presurgery AL data may cause a significant refractive error in RRD-CD patients who underwent PPV.