The aim of this retrospective analysis was to evaluate the clinical and radiographic results of a shortened protocol (using a lateral approach) for early surgical reentry, following a large sinus membrane perforation that occurred during maxillary sinus augmentation (lateral approach), for the rehabilitation of patients with an atrophic posterior maxilla. Between May 2015 and October 2020, seven patients underwent reentry surgery using a lateral approach protocol 1 month after a large sinus membrane perforation during maxillary sinus floor augmentation with lateral approach surgery. All patients presented a residual under-sinus bone height < 3 mm in the posterior maxilla. The sinus membrane was elevated during the reentry surgery, without any difficulty for any patient, using manual blunt elevators or piezoelectric devices, and the sinus floor height was augmented with bone substitute particles. No further perforations were made, and no complications were recorded during the follow-up period from 18 months to 6 years. The 1-month waiting period after the initial sinus surgery allows easy sinus membrane elevation and a lack of complications. This timing could be a feasible option for surgical reentry after a large sinus membrane perforation occurs.