Gingivostomatitis is the most common primary and symptomatic clinical manifestation of HSV-1 infection. Painful oral lesions appear as ulcerative erosions on the gingiva, palate, buccal mucosa, and tongue, leading to eating and drinking difficulties with an evolution between 10-14 days. This paper describes a case of a 19-month-old boy with severe painful Gingivostomatitis lesions. Low level laser therapy (LLLT) was used with an immediate outcome.