Background Extrathyroidal extension of thyroid cancer has the greatest negative impact on patient prognosis among adverse prognostic factors. While resection of locally invasive carcinoma with negative margins offers the best outcome, precise preoperative planning it vital. Routine preoperative evaluation includes ultrasound, with computed tomography (CT) gaining favour for suspicion of local invasion. However, the utility of magnetic resonance imaging (MRI), bronchoscopy and esophagoscopy is less well established. Methods A retrospective case series was conducted on total thyroidectomies performed over an eight-year period (1/1/2017 to 31/12/2024) at Princess Alexandra Hospital, a high-volume thyroid cancer centre in Australia. The study included patients who underwent preoperative CT and MRI and had malignant histopathology. Two independent radiologists assessed the sensitivity and specificity of CT and MRI in detecting extrathyroidal invasion of the trachea, esophagus, and recurrent laryngeal nerve (RLN). The use of preoperative and intraoperative bronchoscopy and esophagoscopy was evaluated. Results 18 patients met inclusion criteria. Both CT and MRI had 100% sensitivity for invasion of all three structures. MRI demonstrated higher specificity for tracheal (57% vs. 50%) and esophageal invasion (64% vs. 57%), while preoperative vocal cord assessment had the highest specificity for RLN invasion (91%). Five patients had a bronchoscopy, of which three correlated with MRI findings. Two patients had an esophagoscopy, both correlating with MRI findings. We present three case studies illustrating how imaging findings influence surgical decision-making, as well as an algorithm for when to consider MRI and bronchoscopy / esophagoscopy. Conclusion Given the complex decision-making required for managing extrathyroidal invasion of critical structures, this presentation offer practical insights to equip surgeons with a structured guideline on preoperative evaluation.