Aim To develop and test the psychometric characteristics of a questionnaire measuring attitudes toward plagiarism. Methods Participants were 227 undergraduates and graduate students (128 women and 99 men) from three Croatian universities, with a median age of 21 years (range 18 to 48). Research was conducted from March to June 2009. For the purpose of construction of the first version of the questionnaire, 67 statements (items) were developed. The statements were based on the relevant literature and were developed following rules and recommendations for questionnaire writing, and 36 items were chosen for final validation. Factor analysis was used to find out the factor structure of the questionnaire and to measure construct validity. Results The final version of the questionnaire consisted of 29 items divided into a three-factor structure: factor I – positive attitude toward plagiarism (12 items) ; factor II – negative attitude toward plagiarism (7 items) ; and factor III – subjective norms toward plagiarism (10 items). Cronbach α was calculated to confirm the reliability of the scale: factor I – α = 0.83 ; factor II – α = 0.79 ; and factor III – α = 0.85. Correlations between factors were: -0.37 between I and II, -0.41 between I and III, and +0.31 between II and III. Conclusion Attitudes Toward Plagiarism questionnaire was developed, with good psychometric characteristics. It will be used in future research as a standardized tool for measuring attitudes toward plagiarism.