OBJECTIVES: 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 (n = 1,009), and 6 (n = 741) 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 women = 11 kg, for men = 12 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 (P < .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 (P < .01) in women and men (β = 0.57, standard error (SE) = 0.18; β = 0.37, SE = 0.16, respectively). Lower serum albumin was also associated with substantial decline in muscle strength in women (per unit albumin (g/L) adjusted odds ratio (OR) = 1.14, one-sided 95% confidence limit (CL) = 1.07) and men (per unit albumin (g/L) adjusted OR = 1.14, 95% CL = 1.08). Similar but slightly weaker associations were found between serum albumin and 6-year change in muscle strength (P < .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.