AbstractAlzheimer's disease (AD) is a common neurodegenerative disorder, and oxidative stress plays a vital role in its progression. Antarctic krill oil (AKO) is rich in polyunsaturated fatty acids, which has various biological activities, such as improving insulin sensitivity, alleviating inflammation and ameliorating oxidative stress. In this study, the protective effect of AKO against AD were investigated in senescence‐accelerated prone mouse strain 8 (SAMP8) mice. Results showed that treatment with AKO could effectively ameliorate learning and memory deficits and ease the anxiety in SAMP8 mice by Morris water maze, Barnes maze test and open‐field test. Further analysis indicated that AKO might reduce β‐amyloid (Aβ) accumulation in hippocampus through decreasing the contents of malondialdehyde (MDA) and 7,8‐dihydro‐8‐oxoguanine (8‐oxo‐G), increasing the superoxide dismutase (SOD) and glutathione peroxidase (GSH‐Px) activities in the brain of SAMP8 mice.Practical ApplicationThe results of Morris water maze, Barnes maze test and open‐field test indicated that Antarctic krill oil (AKO) improved the cognitive function and anxiety of SAMP8 mice. AKO reduced the Aβ42 level in hippocampus of SAMP8 mice. AKO ameliorated oxidative stress in brain rather than in serum and liver of SAMP8 mice.