Background: Population aging is a major health issue in most countries. Sleep is one of the significant factors affecting aging and elderly people's quality of life. The present study was done to assess sleep quality and its contributing factors among elderly people. Methods: This cross-sectional descriptive-analytical study was conducted in 2016 on 284 elderly people aged sixty or more. Participants were selected from healthcare centers located in Birjand city, Iran, via the two-stage cluster sampling method. Data collection tools were a demographic questionnaire and the eighteen-item pittsburg sleep quality index. The collected data were entered into SPSS software (v. 16.0) and analyzed using Mann-Whitney U and Kruskal-Wallis tests at the significance level of less than 0.05.