The purpose of this study was to evaluate the utility of ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (FPCT) parameters for detecting recurrent disease and the outcomes of salvage surgery in patients with locally advanced oral tongue squamous cell carcinoma (TSCC) after multimodal treatment. In total, 69 patients with locally advanced TSCC were treated with multimodal therapy. All patients underwent whole-body FPCT scans 4–10 months after the initial surgery. The analysis included FPCT parameters, such as maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), and total lesion glycolysis (TLG). Histological examination was used as the reference standard. Patients with recurrent TSCC underwent salvage surgery or surgery plus systemic treatment. This study included 69 patients: 36 in the recurrent TSCC group and 33 in the non-recurrent TSCC group. The SUVmax, MTV, and TLG in the recurrent TSCC group were 11.3 ± 3.6, 28.3 ± 15.6 cm³, and 113.2 ± 46.8 g, respectively; these values were 5.9 ± 3.6, 5.1 ± 2.2 cm³, and 13.4 ± 4.8 g, in the non-recurrent TSCC group respectively. The two groups had significant differences in terms of SUVmax, MTV, and TLG. In the recurrent TSCC group, 91.6 % of patients presented with local, locoregional, and regional disease and underwent salvage surgery plus systemic therapy, whereas 8.4 % had locoregional recurrence with distant metastases alone and underwent surgery plus systemic therapy. The patients were followed up for 12–60 months; 19 and 20 patients in the recurrent and non-recurrent TSCC groups showed no evidence of disease, whereas 11 and 8 were alive with the disease. Local recurrence or distant metastases led to the deaths of six patients in the recurrent TSCC group and five in the non-recurrent TSCC group. No significant differences in survival were observed between the two groups. FPCT parameters can detect the recurrence of locally advanced TSCC after multimodal treatment. Early salvage surgery can improve the treatment outcomes for recurrent TSCC.