Background: Activation of the NOTCH signaling pathway is associated with tumorigenesis. The aim of this study was to investigate NOTCH pathway gene functions and regulatory mechanisms in ovarian cancer (OC). Methods: We conducted a bioinformatics analysis of publicly available datasets in order to identify potential NOTCH-related mechanisms, associated genes, biological pathways, and their relation to immune function. Results: Significant differential expression of the NOTCH pathway genes DLL1, DLL3, DLL4, HES1, HEY1, JAG1, NOTCH2, NOTCH3, and NOTCH4 was observed between OC samples and normal controls. Low expression of DLL4 and of NOTCH4 in OC patients was associated with International Federation of Gynecology and Obstetrics (FIGO) stage (p 0.001 and p = 0.036, respectively), while high expression of NOTCH3 was associated with race (p = 0.039) and age (p = 0.044). JAG2 and NOTCH1 expression were significantly associated with progression-free interval (PFI) (p = 0.011 and p = 0.039, respectively). DLL1 (Hazard Ratio (HR): 2.096; 95% CI: 1.522–2.886, p 0.001) and NOTCH1 (HR: 0.711; 95% CI: 0.514–0.983, p = 0.039) expression were independently associated with PFI in multivariate analysis. DLL1, DLL3, JAG1, JAG2, NOTCH3 and NOTCH4 expression could significantly differentiate OC from non-cancer samples. Genes associated with the NOTCH pathway were mainly enriched in five signaling pathways: the NOTCH signaling pathway, breast cancer, endocrine resistance, Th1 and Th2 cell differentiation, and oxidative phosphorylation. The expression of NOTCH pathway genes was significantly associated with immune cell infiltration. Conclusions: NOTCH pathway genes appear to play an important role in the progression of OC by regulating immune cells, endocrine resistance, Th1 and Th2 cell differentiation, and oxidative phosphorylation. JAG2 and NOTCH1 are potential biomarkers and therapeutic targets for the treatment of OC.