Background Insomnia is associated with depression, cognitive impairment, hypertension, myocardial infarction, stroke, metabolic syndrome and prostate cancer in the elderly. The aim of this study is to investigate the relationship between severity of insomnia and falls. Methods This cross-sectional study was conducted in a single geriatric outpatient clinic at a university teaching hospital. Patients with active infection, who could not complete insomnia severity index (ISI) test because of cognitive impairment and who could not perform handgrip strength and timed up and go (TUG) tests were excluded from the study. Results A total of 215 patients were included in this study. Logistic regression analysis showed that there is significant relationship between poorer TUG performance, mild insomnia, moderate insomnia, severe insomnia and falls in the elderly (odds ratio (OR) = 1.04, CI: 1.00-1.09, P = 0.041, OR = 2.43, CI: 1.22-4.85, P = 0.011, OR = 3.84, CI:1.35-10.94, P = 0.012, OR = 5.81, CI:1.00-33.72, P = 0.050). Conclusions In this study we showed that there is a relationship between the severity of insomnia and falls.