Background: Long noncoding RNAs (lncRNAs), as emerging regulators of a wide variety of biological processes via diverse mechanisms, have been demonstrated to be of increasing importance in biology. Genome-wide association studies of tumor samples have identified several lncRNAs as either oncogenes or tumor suppressors in various types of cancers. In recent years, the importance of lncRNAs, especially in endometrioid cancer (EEC), has become increasingly well understood. The lncRNA Forkhead box P4 antisense RNA 1 (FOXP4-AS1) has been reported to fulfill roles in several types of cancers; however, the main biological function and associated underlying molecular mechanism of FOXP4-AS1 in EEC have yet to be fully elucidated. Materials and Methods: The present study therefore aimed to investigate how RNA FOXP4-AS1 may participate in the development and progression of endometrioid carcinoma tissues. To meet this aim, in the present study, the expression level of FOXP4-AS1 was investigated in endometrioid carcinoma tissues and matching nearby normal endometrial tissues collected from patients receiving surgery at the hospital, and a series of molecular biological assays were performed to investigate the effect of FOXP4-AS1 on cell proliferation, cell migration, and cell invasion, and so on. Results: An increased concentration of FOXP4-AS1 was identified in endometrioid carcinoma samples and cell lines compared with the corresponding controls, and this lncRNA was found to be positively correlated with advanced FIGO stages in patients with endometrial cancer. Furthermore, knocking down endogenous FOXP4-AS1 led to a significant reduction in the colony formation number and a significant inhibition of cell proliferation, cell migration, and cell invasion in endometrioid carcinoma cells. Moreover, dual-specificity phosphatase 5 (DUSP5), which is lowly expressed in endometrioid carcinoma tissues cells and negatively modulated by FOXP4-AS1, was identified as the downstream target molecule of FOXP4-AS1. Subsequently, the mechanistic experiments confirmed that, through binding to enhancer of zeste homolog 2 (EZH2; one of the catalytic subunits of polycomb repressive complex 2 [PRC2]), FOXP4-AS1 could epigenetically suppress the expression of DUSP5. Finally, the oncogenic function of the FOXP4-AS1/EZH2/DUSP5 axis in endometrioid carcinoma was confirmed via rescue assays. Conclusions: The findings of the present study have highlighted how FOXP4-AS1 fulfills an oncogenic role in endometrioid carcinoma, and targeting FOXP4-AS1 and its pathway may provide new biomarkers for patients with endometrioid carcinoma.