Despite the research supporting acceleration, some teachers are still hesitant to recommend acceleration for advanced students. The Teacher Attitudes Toward Subject-Specific Acceleration (TATSSA) instrument was designed to uncover the factors that influence teacher decisions to recommend students for subject-specific acceleration. First, we describe the creation of the TATSSA and initial instrument validation process. Then we examine the validity of the established measurement model and explore the construct validity of the TATSSA. Scores on the TATSSA predicted teacher intent to recommend acceleration, were related to teacher past recommendation behavior, and discriminated between groups known to be more or less likely to accelerate. The most important findings were that teacher self-efficacy toward recommending acceleration was universally important in predicting teacher acceleration attitudes and behavior, administrative support of acceleration was critical, and teachers appeared to give more weight to potential negative outcomes of acceleration than positive ones.