Posttraumatic stress disorder (PTSD) is associated with self‐reported difficulties navigating the social and physical world and may also be associated with risk of functional limitations. The Short Physical Performance Battery (SPPB), an objective functional assessment, was administered during monitoring exams between January and December 2015 to a consecutive sample of 1,268 rescue workers, volunteers, and other responders who had aided in response, recovery, and cleanup efforts at the World Trade Center (WTC) in New York after the September 11, 2011 attacks. Data were linked with diagnostic and longitudinal data from the WTC monitoring study. Multivariable analyses were used to examine predictors of functional limitations. Prevalence estimates weighted to the general responder population revealed a relatively high prevalence of functional limitations, SPPB ≤ 9; 16.0%, 95% CI [13.7, 18.4]. Current PTSD was associated with a twofold increased risk of functional limitations after controlling for predisposing factors, trauma severity, behavioral factors, and WTC‐related medical conditions, adjusted risk ratio (aRR) = 2.11, 95% CI [1.48, 3.01]. Exposure to ergonomic risk factors at the WTC also increased the risk of functional impairments, aRR = 1.34 95% CI [1.05, 1.70]. Longitudinal results suggest that individuals with current functional limitations experienced high baseline PTSD severity, B = 2.94, SE = 1.33, and increasing PTSD symptom severity, B = 0.29, SE = 0.10, since September 11, 2001. This study identified a cross‐sectional relationship between functional limitations and PTSD and a worsening of PTSD symptoms in persons who eventually demonstrated functional limitations. Results highlight the potential role of chronic PTSD in functional limitations.