To examine whether low serum albumin is associated with low muscle strength and future decline in muscle strength in community-dwelling older men and women. Design: Population-based cohort study. Setting: The Longitudinal Aging Study Amsterdam. Participants: Six hundred seventy-six women and 644 men aged 65 to 88. Measurements: Serum albumin was determined at baseline. Muscle strength was assessed using grip strength at baseline, after 3 (n51,009), and 6 (n5741) years. The outcomes were continuous baseline muscle strength, 3- and 6-year change in muscle strength, and a dichotomous indicator for substantial decline (a decrease if _1 standard deviations for women511 kg, for men512 kg) in muscle strength. Results: Mean serum albumin concentration _ standard deviation was 45.0 _ 3.3 g/L for women and 45.2 _ 3.2 g/L for men. At baseline, adjusting for age, lifestyle factors, and chronic conditions, lower serum albumin was cross-sectionally associated with weaker muscle strength (Po.001) in women and men. After 3 years of follow-up, mean decline in muscle strength was _5.6 _ 10.9 kg in women and _9.6 _ 11.9 kg in men. After adjustment for potential confounders, lower serum albumin was associated with muscle strength decline over 3 years (Po.01) in women and men (b50.57, standard error (SE)5 0.18; b50.37, SE50.16, respectively). Lower serum albumin was also associated with substantial decline in muscle strength in women (per unit albumin (g/L) adjusted odds ratio (OR)51.14, one-sided 95% confidence limit (CL)51.07) and men (per unit albumin (g/L) adjusted OR51.14, 95% CL51.08). Similar but slightly weaker associations were found between serum albumin and 6-year change in muscle strength (Po.05). Conclusion: These results suggest that low serum albumin, even within the normal range, is independently associated with weaker muscle strength and future decline in muscle strength in older women and men.