The functional integrity of the floor of the mouth (FOM) is essential in maintaining tongue mobility, deglutition, and control and disposal of saliva. The present study focused on reporting oral function using functional intraoral Glasgow scale (FIGS) in patients who had surgical ablation and reconstruction of FOM carcinoma with or without chemo-radiotherapy. The study included patients who had surgical treatment of floor of mouth cancer in two regional head and neck units in Glasgow, UK between January 2006 and August 2007. Patients were assessed using FIGS before surgery, 2 months, 6 months and 1 year after surgery. It is a five-point scale self-questionnaire to allow patients to self-assess speech, chewing and swallowing. The maximum total score is 15 points. The influence of socio-demographic parameters, tumour characteristics and surgical parameters was addressed in the study. A total of 62 consecutive patients were included in the study; 41 (66.1 %) were males and 21 (33.9 %) were females. The patients' mean age at the time of diagnosis was 60.6 years. Fifty (80.6 %) patients had unilateral origin of FOM tumours and 10 (19.4 %) had bilateral origin. Peroral approach was the most common approach used in 35 (56.4 %) patients. The mean preoperative FIGS score was 14. Two months after surgery, it droped to 9.4 then started to increase gradually thereafter and recorded 10.1 at 6 months and 11 at 1 year. Unilateral FOM resection recorded better score than bilateral and lateral FOM tumours than anterior at 1 year postoperatively. Furthermore, direct closure showed better functional outcome than loco-regional and free flaps. The FIGS is a simple and comprehensive way of assessing a patient's functional impairment following surgery in the FOM. Tumour site and size, surgical access, surgical resection and method of reconstruction showed significant influence on oral function following surgical resection. A well-designed rehabilitation programme is required to improve oral function after surgical resection of oral cancer.