BACKGROUND: Primary leiomyosarcoma of the tongue is an extremely rare malignant mesenchymal tumour that exhibits smooth muscle differentiation. Only 23 cases of this neoplasm have been described in the literature. CASE REPORT: This article describes a case report of a primary leiomyosarcoma of the right lateral border of the tongue in a 35-year-old male. The diagnosis was supported by histological findings and immunohistochemical positivity for desmin, vimentin and smooth muscle actin. Hemiglossectomy with supraomohyoid neck dissection was done with three years follow-up, without evidence of local recurrence or distant metastasis. The available literature has been reviewed for a better understanding of this rare neoplasm. CONCLUSION: Leiomyosarcoma in this unusual site seems to have a better prognosis than elsewhere, although the number of cases are too small to draw a conclusion. Further research with longer follow-up is required to better understand this rare pathological entity.