Background/Objectives: Primary hyperparathyroidism (PHPT) is most commonly caused by a single cervical parathyroid adenoma; however, a minority of cases originate from ectopic glands, including intrathoracic localizations. Intrathoracic ectopic parathyroid glands (EPGs) are rare and pose significant diagnostic and therapeutic challenges due to their anatomical variability and overlap with other mediastinal pathologies. Methods: We retrospectively analyzed 13 consecutive patients with PHPT caused by intrathoracic EPGs, who underwent minimally invasive surgical resection between 2015 and 2024 at two Italian tertiary referral centers. Demographic characteristics, biochemical profiles, imaging findings, surgical approaches, intraoperative parathyroid hormone (ioPTH) kinetics, and postoperative outcomes were evaluated. Results: All patients underwent successful resection using video-assisted thoracoscopic surgery (VATS) or robotic-assisted thoracoscopic surgery (RATS). Ectopic glands were identified in thymic, mediastinal, retroesophageal, paratracheal, and aortopulmonary locations. Postoperative normalization of calcium, phosphate, and PTH levels confirmed biochemical cure in all patients. No intraoperative complications or 30-day mortality were observed. Higher preoperative PTH levels were associated with longer operative times only in an exploratory, non-significant manner. Conclusions: Intrathoracic EPGs should be suspected in patients with PHPT and negative cervical imaging. Minimally invasive thoracic surgery provides safe and effective treatment with excellent biochemical outcomes. Elevated preoperative PTH levels may reflect increased surgical complexity, a hypothesis that warrants validation in larger cohorts.