Haemangiomas (HAs) are prevalent vascular endothelial cell tumours. With respect to the possible involvement of HIF-1α in HAs, we have explored its role in haemangioma endothelial cell (HemEC) proliferation and apoptosis. shRNA HIF-1α and pcDNA3.1 HIF-α were manipulated into HemECs. HIF-α, VEGF, and VEGFR-2 mRNA and protein levels were assessed by qRT-PCR and Western blotting. Cell proliferation and viability, cell cycle and apoptosis, migration and invasion, and ability to form tubular structures were assessed by colony formation assay, CCK-8, flow cytometry, Transwell assay, and tube formation assay. Cell cycle-related protein levels, and VEGF and VEGFR-2 protein interaction were detected by Western blot and immunoprecipitation assays. An Haemangioma nude mouse model was established by subcutaneous injection of HemECs. Ki67 expression was determined by immunohistochemical staining. HIF-1α silencing suppressed HemEC neoplastic behaviour and promoted apoptosis. HIF-1α facilitated VEGF/VEGFR-2 expression and the VEGF had interacted with VEGFR-2 at protein - protein level. HIF-1α silencing arrested HemECs at G0/G1 phase, diminished Cyclin D1 protein level, and elevated p53 protein level. VEGF overexpression partially abrogated the effects of HIF-1α knockdown on inhibiting HemEC malignant behaviours. Inhibiting HIF-1α in nude mice with HAs repressed tumour growth and Ki67-positive cells. Briefly, HIF-1α regulated HemEC cell cycle through VEGF/VEGFR-2, thus promoting cell proliferation and inhibiting apoptosis.© 2023 Company of the International Journal of Experimental Pathology (CIJEP).