Background Image‐guided surgery could help obtain clear (≥5.0 mm) resection margins. This feasibility study investigated ultrasound‐guided resection accuracy of buccal mucosa squamous cell carcinoma (BMSCC). Methods MRI and ultrasound measurements of tumor thickness were compared to histology in 13 BMSCC‐patients. Ultrasound measured margins (at five locations) on the specimen were compared to the corresponding histological margins. Results Accuracy of in‐ and ex‐vivo ultrasound (mean deviation from histology: 1.6 mm) for measuring tumor thickness was comparable to MRI (mean deviation from histology: 2.6 mm). The sensitivity to detect clear margins using ex‐vivo ultrasound was low (48%). If an ex‐vivo ultrasound cutoff of ≥7.5 mm would be used, the sensitivity would increase to 86%. Conclusions Ultrasound‐guided resection of BMSCC's is feasible. In‐ and ex‐vivo ultrasound measure tumor thickness in BMSCC accurately. We recommend ≥7.5 mm resection margins on ex‐vivo ultrasound to obtain histological clear margins. Additional research is required to establish the effect of 7.5 mm ultrasound cutoff.