AbstractObjective: To study whether walking limitation at old age is determined by obesity history.Research Methods and Procedures: In a retrospective longitudinal study based on a representative sample of the Finnish population of 55 years and older (2055 women and 1337 men), maximal walking speed, body mass, and body height were measured in a health examination. Walking limitation was defined as walking speed <1.2 m/s or difficulty in walking 0.5 km. Recalled height at 20 years of age and recalled weight at 20, 30, 40, and 50 years of age were recorded.Results: Subjects who had been obese at the age of 30, 40, or 50 years had almost a 4‐fold higher risk of walking limitation compared to non‐obese. Obesity duration increased the age‐ and gender‐adjusted risk of walking limitation among those who had been obese since the age of 50 (odds ratio, 4.33; 95% confidence interval, 2.59 to 7.23, n = 114), among the obese since the age of 40 [6.01 (2.55 to 14.14), n = 39], and among the obese since the age of 30 [8.97 (3.06 to 26.29), n = 14]. The risk remained elevated even among those who had previously been obese but lost weight during their midlife or late adulthood [3.15 (1.63 to 6.11), n = 71].Discussion: Early onset of obesity and obesity duration increased the risk of walking limitation, and the effect was only partially mediated through current BMI and higher risk of obesity‐related diseases. Preventing excess weight gain throughout one's life course is an important goal in order to promote good health and functioning in older age.