Galectins are carbohydrate-binding proteins that function to regulate immune and inflammatory response. The expression of galectin genes LGALS1, LGALS3, and LGALS9 has been associated with innate and adaptive immunity. Bioactive plant-derived polyphenols enhance immunological health in animals. Studies have shown that bioactive plant compounds are able to bind and regulate galectins in inflammatory diseases. Polyphenols derived from Moringa oleifera have antioxidant and anti-inflammatory properties but their effect on galectin expression in the bovine peripheral blood mononuclear cells (PBMC) has not been studied. The objective of this study was to investigate the effects of Moringa oleifera polyphenol extract (MOPE) on galectin gene transcription and translation in LPS-challenged bovine PBMC ex vivo. Bovine PBMC was isolated from blood collected from lactating Holstein cows (n = 10; age = 3.73 ± 0.35 yr, milk yield = 25.71 ± 3.11 kg/cow per day) using Ficoll technique. LPS-challenged PBMC (1.0 μg/mL Escherichia coli O111:B4), was incubated with MOPE (10 μg/mL) for 3 h. Quantitative real-time PCR (qRT-PCR) was used to evaluate the mRNA levels of bovine galectin 1 (LGALS1), galectin 3 (LGALS3), and galectin 9 (LGALS9), using TBP, ACTB, and RPLP0 as internal controls. Secretion of GAL-1, GAL-3, and GAL-9 in culture supernatant was measured using ELISA. Data were analyzed by GLM procedure (SAS 9.4). Results from the qRT-PCR showed decreased mRNA of LGALS1 (fold change, FC = −2.01), LGALS3 (FC = −3.84) and LGALS9 (FC = −3.98) after treatment with MOPE. Treatment with MOPE decreased mean concentration of GAL-1 (41.71 vs. 172.76 ng/mL; P < 0.01), GAL-3 (3.30 vs. 9.95 ng/mL; P < 0.01) and GAL-9 (854.05 vs. 2336.76 pg/mL; P < 0.01). Overall, results from this study showed that polyphenol from Moringa decreased GAL-1, GAL-3 and GAL-9 mRNA and protein expression in bovine PBMC. Our finding suggest the use of polyphenols extract from Moringa enriched feed supplements may have immunomodulatory properties for bovine health, and aid in the design of galectin-based strategy to counteract LPS-induced inflammation and morbidities.