Associations of objectively measured physical activity (PA) with objectively measured lower limb function in adults age 70 and older were studied. Lower limb function was assessed using the Short Physical Performance Battery (SPPB) and PA by an accelerometer providing mean daily counts per minute (CPM), mean daily steps and minutes of moderate or vigorous PA (MVPA) per day. A minority (32 [13%]) scored low (≤6 out of a maximum of 12) on the SPPB, but only 3 (1%) achieved recommended PA levels. Adjusting for confounders, the odds ratio of low SPPB (≤6) comparing those in the lowest one third to highest two thirds of mean CPM was 55 (95%CI: 6, 520); for mean steps per day it was 23 (95%CI: 4, 137) and for minutes of MVPA per day 56 (95%CI: 6, 530). Low levels of PA are common and are associated with poor levels of lower limb function in older adults.