Aim The associations of body mass index (BMI) and serum lipids with cognitive function are inconsistent and remain unclear, especially in the elderly population. This discrepancy triggered our interest in exploring the impact of BMI and serum lipids on memory status among the elderly Chinese population. Methods Data were collected from the China Health and Nutrition Survey database. We used data from the survey's 2015 wave to examine the association between BMI and memory status and from the 2009-2015 surveys to examine the association between serum lipids and cognitive function. We performed multivariable logistic regression analyses and multivariable linear regression analyses to examine these associations. Results Being underweight, normal weight, and severely obese were associated with an increased risk of bad self-reported memory status, with overweight as the reference. After adjustment for confounding factors, BMI was positively associated with cognitive function score in the low BMI group (<= 24.5 kg/m(2)) (beta +/- SE: 0.02 +/- 0.01, P = 0.013) and negatively associated with cognitive function score in the high BMI group (>24.5 kg/m(2)) (beta +/- SE: -0.04 +/- 0.01, P = 0.009) in multivariable linear regression analysis. In men, higher levels of serum triglycerides and apolipoprotein B were associated with a decreased risk of cognitive impairment. In women, a higher level of high-density lipoprotein cholesterol was associated with a decreased risk of cognitive impairment. Conclusion We found inverse U-shaped relationships between BMI and cognitive function and for the gender-specific association of serum lipids with cognitive function. This result indicated that among the elderly population, better nutritional status suggests superior memory status and cognitive function performance.