The IER3 gene has a complex role in cancer biology, acting either as a tumor suppressor or an oncogene, depending on the cancer type. This duality underscores the complexity and importance of molecular pathways in modulating cancer behavior. Despite its significance in cancer development, there is a dearth of studies elucidating the exact mechanisms underlying IER3’s involvement in modulating cancer behavior. Here, utilizing cervical carcinoma and neuroblastoma (NB) cell lines as model systems we characterized the pathways that mediate the functional switch between the oncogenic and tumor suppressor roles of IER3. In HeLa cells, IER3 expression promotes an oncogenic program that includes immediate early response pathway genes such as EGR2, FOS, and JUN. However, in NB cells, IER3 suppresses the EGR2-dependent oncogenic program. This differential regulation of EGR2 by IER3 involves epigenetic modulation of the EGR2 promoter. IER3 dependent tumor suppressor pathway in NB cells relies on ADAM19 gene. Thus, our findings uncover the molecular pathways that dictate the context-dependent roles of IER3 in cancer, providing insights into its dual functionality in different cancer types.