Background: According to the World Health Organization (WHO), oral cancer is one of the most common malignancies of the head and neck region, ranking 16th among all cancers worldwide. Approximately 90% of oral cancers are oral squamous cell carcinomas. The development of this malignancy is influenced by multiple factors, and some genes plays a crucial role in development of the cancer. In recent years, the potential association between lncRNA GSEC and cancer has attracted significant research interest. Aim: This study aimed to investigate some functions of lncRNA GSEC in oral squamous cell carcinoma (OSCC) in vivo experimental model. Materials and Methods: To examine the role of GSEC in the proliferation of human oral cancer cells (CAL27), fifteen healthy 5-week-old BALB/c nude mice were divided into three groups: group Blank (CAL27 cells alone), NC (control si-NC CAL27 cells), and si-GSEC (si-GSEC CAL27 cells). The mice were subcutaneously injected with CAL27 cells alone, control si-NC CAL27 cells and si-GSEC CAL27 cells. Body weight and tumor size of the mice were measured throughout the experiment. On day 13, the mice were sacrificed, tumor tissues were excised and weighed, and the tumor tissues were stained using hematoxylin–eosin (HE) and immunohistochemistry to examine the expression of proliferation-related proteins Ki-67 and PCNA. Results: No significant differences in body weight were observed among the three groups of the mice up to day 13. However, the excised tumors from the si-GSEC CAL27 group were significantly smaller and lighter than those from the si- NC CAL27 and CAL27-only groups (p < 0.001). HE staining showed that tumor tissues in the si-GSEC group had more organized structure, better cellular differentiation, fewer malignant cells, decreased nuclear division, and reduced tumor transformation compared with the other groups. Immunohistochemical analysis revealed that Ki-67 and PCNA expression in tumor tissues was heterogeneously distributed, with higher density in peripheral and poorly differentiated regions, and lower expression in keratinized and necrotic areas. Notably, expression levels of both Ki-67 and PCNA were markedly reduced in the si-GSEC group compared with the other two groups. Conclusion lncRNA GSEC promotes tumor cell proliferation in vivo in oral squamous cell carcinoma.