This study evaluated effects of diet supplementation with omega-3 polyunsaturated fatty acids (PUFA) from microalgae on boar sperm quality. Two groups of boars (n = 3 each) were fed during 75 days either a commercial diet (control), or the same diet supplemented with omega-3 PUFA from the heterotrophic microalgae Schizochytrium sp. (120 g/kg). Sixteen ejaculates were collected per boar. Some sperm kinetics parameters were inferior for supplemented than for control boars (p < .05): distance average path; distance in both curved and straight line; velocity average path, velocity in both curved and straight line; and amplitude of lateral head displacement. Spermatozoa from supplemented boars presented lower mitochondrial functionality, but greater membrane fluidity compared to the control group (p < .01). Membrane and acrosome integrity, production of reactive oxygen species and lipid peroxidation did not differ (p > .05). Serum cholesterol levels were greater (p < .05) for supplemented than for control boars at the 30th and 60th d of supplementation, but levels of triglycerides and IGF-1 did not differ (p > .05). Compared to the control, spermatozoa of supplemented boars were slower, travelled shorter distances and presented impaired energy metabolism, but their greater membrane fluidity may potentially favour their cryopreservation.