This study compares the functional mobility of 2290 community residents (aged 70-79 years and participating in the Health, Aging, and Body Composition study) by thyroid function categorized by thyrotropin level as euthyroid or mild or moderate subclinical hypothyroid (SCH). In age- and sex-adjusted analyses, the mild SCH group, compared with the euthyroid group, demonstrated better mobility (faster usual and rapid gait speed [1.20 vs 1.15 m/s and 1.65 vs 1.56 m/s, respectively; P < .001]) and a higher percentage had good cardiorespiratory fitness and reported walking ease (39.2% vs 28.0% and 44.7% vs 36.5%, respectively; P < .001). After 2 years, the mild SCH group experienced a similar decline as the euthyroid group but maintained their mobility advantage. The moderate SCH group had similar mobility and decline as the euthyroid group. Findings indicate that generally well-functioning 70- to 79-year-old SCH individuals do not demonstrate increased risk of mobility problems and those with mild elevations in thyrotropin level show a slight functional and possible health advantage.