Patients surgically treated for oral cancer are affected by several underestimated deglutition disorders risk factors. This study aims to characterize the level of these food oral processing (FOP) impairments in a group of patients treated by surgery for tongue cancer. Twenty-seven consecutive patients surgically treated for tongue cancer were evaluated concerning their chewing capacity (Mastication-test), and responded to questions concerning their capacity to bite, chew and manipulate food with their tongue, and their quality of life. According to the Mastication-test, 16 patients suffered total FOP incapacities (TI group), characterized by high tumor stage, invasive carcinological surgery and necessity of reconstructive surgery; 12 patients were partially or not impaired (PI/NI-group). Tongue movement score and number of dental units were lower in the TI group than in the PI/NI-group. Subjective FOP criteria were clearly impaired in the TI group and correlated with a poor oral health-related quality of life. One year after surgery, there is a decrease in BMI for TI group patients while the PI group patients had a significant increase in BMI. All patients surgically treated for oral cancer suffered FOP impairments, but not with the same severity. Totally impaired subjects are at higher risk from long-term malnutrition. Functional evaluation of FOP should form part of the post-operative follow-up for all patients suffering from tongue cancer, using a quick combined evaluation of chewing efficiency, oral health quality of life and nutritional status.