Background/Objectives: Third-ventricle colloid cysts are benign but can cause obstructive hydrocephalus and sudden deterioration, and the role of microsurgical transcallosal resection in the endoscopic era remains debated. We evaluated clinical, radiological, and functional outcomes of microscope-assisted interhemispheric transcallosal resection and the effect of preoperative hydrocephalus on recovery. Methods: This retrospective, observational, single-center study analyzed 30 patients with symptomatic, histopathologically confirmed colloid cysts operated on between June 2015 and February 2021, divided into hydrocephalus (n = 16) and non-hydrocephalus (n = 14) groups. Functional outcomes were assessed using the Karnofsky Performance Status (KPS) scale. Results: Mean KPS improved from 65.3 ± 21.0 to 92.0 ± 11.0 (p < 0.001). Patients with hydrocephalus had lower preoperative Glasgow Coma Scale (GCS; p = 0.022) and KPS (p = 0.048) scores, comparable postoperative KPS (p = 0.208), and greater KPS improvement (p = 0.012). Four patients (13.3%) needed external ventricular drainage; none required a permanent shunt. Four patients (13.3%) developed new persistent neurological events (seizures, n = 3; memory impairment, n = 1). No recurrence occurred over a median follow-up of 7.0 years. Conclusions: Microscope-assisted interhemispheric transcallosal microsurgical resection was associated with significant KPS improvement, no permanent shunt requirement, and no recurrence. Despite the increasing use of endoscopic techniques, microsurgical approaches remain valuable due to direct visualization, bimanual dissection, and the potential for durable gross-total resection; however, neurocognitive outcomes were not assessed, and prospective studies are needed.