The goals of this cross-sectional study were to explore correlates of walking speed in a large wide age-ranged population and to identify factors affecting lower walking speed at older ages. Participants were 3,872 community-dwelling adults in the first follow-up of the SardiNIA study who completed a 4-m walking test. Sex-specific correlates of walking speed included marital status, height, waist circumference, pulse wave velocity, comorbidity, subjective health, strength, and personality. Effect modifiers of the age-walking speed association included extraversion (<55 years, p = .019) and education (<55 years, p = .021; > or =55 years, p = .012) in women, and openness (<55 years, p = .005), waist circumference (<55 years, p = .010), and subjective health (<55 years, p = .014) in men. The strong impact of personality suggests that certain personality traits may be associated with behaviors that affect physical performance and condition the reduced mobility mostly at younger ages. If these patterns are confirmed in longitudinal studies, personality may be an important target for prevention.