In this article, we present a valid and reliable instrument which measures the attitude of in-service and pre-service primary teachers toward teaching science, called the Dimensions of Attitude Toward Science (DAS) Instrument. Attention to the attitudes of primary teachers toward teaching science is of fundamental importance to the professionalization of these teachers in the field of primary science education. With the development of this instrument, we sought to fulfill the need for a statistically and theoretically valid and reliable instrument to measure pre-service and in-service teachers' attitudes. The DAS Instrument is based on a comprehensive theoretical framework for attitude toward (teaching) science. After pilot testing, the DAS was revised and subsequently validated using a large group of respondents (pre-service and in-service primary teachers) ("N" = 556). The theoretical underpinning of the DAS combined with the statistical data indicate that the DAS possesses good construct validity and that it proves to be a promising instrument that can be utilized for research purposes, and also as a teacher training and coaching tool. This instrument can therefore make a valuable contribution to progress within the field of science education. (Contains 3 tables and 2 figures.)