INTRODUCTION: The purposes of this study were to identify trajectories of older adults' television viewing (TV) time for 12 yr and to examine their associations with performance-based measures of physical function. METHODS: Data on TV time (h·wk) and sociodemographic factors were collected at each assessment of the Australian Diabetes, Obesity and Lifestyle Study (1999/2000, 2004/2005, and 2011/2012), with objective measures of physical function (2.44 m timed up and go [TUG, s] and knee extensor strength [KES, kg] tests) collected at the final (2011/2012) assessment. Regression analyses examined predictors of trajectory membership and associations with TUG and KES in those 60+ yr of age in 2011/2012. RESULTS: Six TV time trajectories were identified among the 1938 participants (age, 60-97 yr; 54% female): consistently low (9.7%), low-increasing (22.3%), moderate-decreasing (13.5%), moderate-increasing (30.3%), consistently high (18.9%), and high-increasing (5.2%). There were no statistically significant relationships with TUG (P > 0.05). In the fully adjusted model, KES performance was significantly better in the consistently low, low-increasing, and consistently high trajectories, compared with the moderate-increasing trajectory (P < 0.001, R = 0.33). CONCLUSION: Twelve-year trajectories of TV time were associated with muscle strength in older adults. These findings suggest that patterns of sedentary behavior can be a determinant of muscle strength in later life.