Our previous study implied a correlation of inhibitors of differentiation-1 (Id-1) to cervical cancer development. However, how Id-1 contributes to cervical carcinogenesis is unknown. In the present study, we investigated the role of Id-1 in transforming cervical cells with an in vitro transformation model. The human papillomavirus (HPV) immortalized cervical epithelial cells (H8) were successfully transformed by exposure to the carcinogen N-nitrosopyrrolidine (NPYR). The results showed that both Id-1 RNA and protein expression were significantly increased in transformed H8 cells, suggesting a possible role of Id-1 in cervical cell transformation. Ectopic expression of Id-1 in H8 cells potentiated NPYR-induced cell transformation. In contrast, silencing of Id-1 suppressed NPYR-induced H8 cell transformation. A cDNA microarray assay was performed, which identified suggested potential cell signaling pathways for NPYR-induced H8 cell transformation. The results suggest that Id-1 plays an oncogenic role in the cervix, which sheds light on cervical cancer development and implies potential target for cervical cancer prevention and therapy.