This article describes the steps and phases involved in constructing a questionnaire on the motivation to learn a second or foreign language (or L2 motivation). It evaluates psychometric properties of the instrument by performing exploratory and confirmatory factor analyses. Participants in this study were 194 students. The results of the exploratory factor analysis indicated that four dimensions formed the construct of L2 motivation, namely Instrumental orientation, Integrative orientation, Commitment and Effort. The findings from a subsequent confirmatory factor analysis validated the four-dimensional structure. The conclusions reached by this study as well as the steps and phases involved in the development of research instrument on L2 motivation could be informative for educators interested in issues related to language learning motivation and useful for future scholarly investigations of L2 motivation.