Untreated pain is a major health care issue and very little is known about the treatment of pain and the effect of pain on post-operative outcomes in older adults. This study was performed to identify the impact of pain on outcomes following hip fracture in older adults. Four hundred and eleven consecutive cognitively intact patients admitted with hip fracture to four New York hospitals were enrolled in a prospective cohort study. Patients were interviewed daily using standardized pain assessments. We used multiple logistic regression and ordinary least squares linear regression to examine the association of post-operative pain on immediate post-operative outcomes (duration of stay, physical therapy sessions missed or shortened, ambulation following surgery, and post-operative complications) and outcomes 6 months following fracture (locomotion, mortality, return to the community, residual pain). Patients with higher pain scores at rest had significantly longer hospital lengths of stay (P=0.03), were significantly more likely to have physical therapy sessions missed or shortened (P=0.002), were significantly less likely to be ambulating by post-operative day 3 (P<0.001), took significantly longer to ambulate past a bedside chair (P=0.01), and had significantly lower locomotion scores at 6 months (P=0.02). Pain at rest was not significantly associated with post-operative complications, nursing home placement, survival at 6 months, or residual pain at 6 months. Post-operative pain is associated with increased hospital length of stay, delayed ambulation, and long-term functional impairment. Whereas appropriate caution is warranted in administering opioid analgesics to older adults, these data suggest that improved pain control may decrease length of stay, enhance functional recovery, and improve long-term functional outcomes.