This study details the development and initial validation of a 16-item psychometric instrument measuring college students’ motivation for mathematics. The Motivation for Mathematics Abbreviated Instrument (MMAI) consists of four factors (intrinsic motivation, mastery orientation, performance orientation, and expectancy) that were derived from three predominant motivation theories: self-determination, achievement goal, and expectancy value. The instrument development process began with an initial pool of 107 items from existing motivational measures. Input from members of the American Education Research Association (AERA) Special Interest Group (SIG) for Motivation in Education, interviews with students and instructors, and factor analyses of a preliminary (n = 186 post-secondary students) and final administration (n = 386 post-secondary students) of the instrument were used to create the final version of the 16-item measure. Qualitative analyses verified content. Results of the confirmatory factor analyses indicated acceptable fit of the 16-item four-factor model and measurement invariance by gender. We found strong composite reliability. Average variance extracted revealed acceptable internal validity. We conclude that the MMAI is a brief, psychometrically sound measure of motivation that provides a practical and useful tool for classroom-based research into motivation for mathematics.