This article describes the development and validation of the Attitudes toward Sustainable Development scale, a quantitative 20-item scale that measures Italian university students' attitudes toward sustainable development. A total of 484 undergraduate students completed the questionnaire. The validity and reliability of the scale was statistically tested by computing the KMO and Bartlett tests and via an exploratory factor analysis, descriptive statistics, Cronbach's alpha, a confirmatory factor analysis and a multi-group invariance testing. The results of the principal components factor analysis show that the scale consists of the following four dimensions, with five items in each: environment, economy, society and education. The overall structure and measurement of the scale are confirmed by the confirmatory factor analysis and by the multi-group invariance testing. Internal reliability, which was found using Cronbach's alpha, varies between 0.660 and 0.854. The results show that the instrument meets the validity and reliability criteria. To demonstrate its utility, the scale was applied to detect differences in sustainable development attitudes among students pursuing degrees in psychology and in agriculture. Relevant differences were detected for the dimensions of environment and society. The Attitudes toward Sustainable Development scale could be useful for understanding the ways in which students think about sustainability issues and could be used to investigate the relationship between sustainability attitudes and other variables.