Early postoperative nodal recurrence (EPNR) of oral squamous cell carcinoma (OSCC) is not uncommon. Such recurrences may change the intent of treatment and/or volumes of radiotherapy. Contrast-enhanced computed tomography (CECT), magnetic resonance imaging (MRI), and positron emission tomography (PET) have a similar ability to detect lymph node metastasis. However, obtaining postoperative imaging for detecting early recurrence and the initiation of postoperative radiotherapy (PORT) are competing priorities. Hence, we assessed the feasibility of simulation computed tomography (CTSim) for the detection of EPNR in OSCC. CECTSim of 5-mm slice thickness with thermoplastic immobilization was performed in 21 consecutive postoperative patients with OSCC. Treating radiation oncologists and trained radiologists used CECTSim to screen and evaluate the presence of early regional lymph node recurrence. Six out of twenty-one consecutive postoperative OSCC patients had radiological evidence of EPNR on CECTSim. Except for one patient, all EPNRs were limited to contralateral level 1–3 regional nodes in this small series of postoperative OSCC patients. The detection of EPNR on CECTSim necessitated a change in the radiation treatment volume and the corresponding prescribed dose to the target volume. CECTSim may be helpful in the detection of EPNR in OSCC and may preclude the need for additional imaging before the start of PORT. CECTSim may also facilitate the appropriate determination of the radiation volume and appropriate dose to the corresponding target volume.