© The Author(s) 2017. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. Background Lifestyle interventions have been shown to improve physical function over the short term; however, whether these benefits are sustainable is unknown. The long-term effects of an intensive lifestyle intervention (ILI) on physical function were assessed using a randomized post-test design in the Look AHEAD trial. Methods Overweight and obese (body mass index ≥ 25 kg/m 2) middle-aged and older adults (aged 45-76 years at enrollment) with type 2 diabetes enrolled in Look AHEAD, a trial evaluating an ILI designed to achieve weight loss through caloric restriction and increased physical activity compared to diabetes support and education (DSE), underwent standardized assessments of performance-based physical function including a 4- and 400-m walk, lower extremity physical performance (expanded Short Physical Performance Battery, SPPB exp), and grip strength approximately 11 years postrandomization and 1.5 years after the intervention was stopped (n = 3,783). Results Individuals randomized to ILI had lower odds of slow gait speed (<0.8 m/s) compared to those randomized to DSE (adjusted OR [95% CI]: 0.84 [0.71 to 0.99]). Individuals randomized to ILI also had faster gait speed over 4- and 400-m (adjusted mean difference [95% CI]: 0.019 [0.007 to 0.031] m/s, p =.002, and 0.023 [0.012 to 0.034] m/sec, p <.0001, respectively) and higher SPPB exp scores (0.037 [0.011 to 0.063], p =.005) compared to those randomized to DSE. The intervention effect was slightly larger for SPPB exp scores among older versus younger participants (0.081 [0.038 to 0.124] vs 0.013 [-0.021 to 0.047], p =.01). Conclusions An intensive lifestyle intervention has modest but significant long-term benefits on physical function in overweight and obese middle-aged and older adults with type 2 diabetes. ClinicalTrials.gov Identifier NCT00017953.