Background: Dilated cardiomyopathy (DCM) is a severe manifestation or intermediate stage of cardiovascular disease progression with a significantly poor prognosis. Based on a protein interaction network and molecular docking, the present study determined the genes and mechanism of action of angiotensin-converting enzyme inhibitors (ACEIs) in the treatment of DCM, providing a direction for future studies on ACEI drugs for DCM. Methods: This is a retrospective study. DCM samples and healthy controls were downloaded from the GSE42955 dataset, and the targets of the potential active ingredients were obtained from PubChem. Hub genes in ACEIs were analyzed by constructing network models and a protein-protein interaction (PPI) network using the STRING database and Cytoscape software. Molecular docking was performed using Autodock vina software. Results: Twelve DCM samples and five control samples were finally included. A total of 62 intersected genes were obtained by intersecting the differentially expressed genes with six ACEI target genes. PPI analysis identified 15 intersecting hub genes from these 62 genes. Enrichment analysis showed that the hub genes were associated with T helper type 17 (Th17) cell differentiation as well as the nuclear factor kappa-B (NF-kappa B), interleukin 17 (IL-17), mitogen-activated protein kinase (MAPK), tumor necrosis factor (TNF), phosphatidylinositol 3 kinase (PI3K)/protein kinase B (AKT) (PI3K-Akt), and Toll-like receptor signaling pathways. Molecular docking indicated that the compound Benazepril to produce favorable interactions with TNF proteins with a relatively higher score (-8.3). Conclusions: This study primarily revealed that the preventive and curative effects of ACEI treatment on DCM could be realized through multiple targets and pathways, and its mechanism of action is related to genes such as TNF, vascular endothelial growth factor A (VEGFA), interleukin 6 (IL6), C-C motif chemokine ligand 2 (CCL2), Cyclin D1 (CCND1), and AKT serine/threonine kinase 1 (AKT1), with immune-and inflammation-related signaling pathways involvement.