Background: This study aimed to describe the technical characteristics and clinical efficacy of intracranial-to-intracranial (IC-IC) bypass for the treatment of complex intracranial aneurysms. Methods: We retrospectively reviewed all patients with aneurysms who underwent a preplanned combination of surgical or endovascular treatment and IC-IC bypass at our institution between January 2006 and September 2023. IC-IC bypass techniques included four strategies: type A (end-to-end reanastomosis), type B (end-to-side reimplantation), type C (in situ side-to-side anastomosis), and type D (IC-IC bypass with a graft vessel). Results: We performed the type A strategy on five patients (50.0%), type B on one (10.0%), type C on one (10.0%), and type D on three (30.0%). During a mean period of 68.3 months, good clinical outcomes (modified Rankin Scale score, 0-2) were observed in all patients. Follow-up angiography demonstrated complete aneurysmal obliteration in all patients and good bypass patency in nine of ten patients (90.0%). Conclusions: The treatment of complex aneurysms remains a challenge with conventional surgical or endovascular treatments. IC-IC bypass surgery is a useful technique, associated with favorable clinical outcomes, for treating complex aneurysms.