As learning is a product of the interaction between certain concepts which are already present within an individual's mind, it is becoming increasingly important to determine the cognitive structures in relation to these concepts which are present within the minds of students. It has been said that the word association test, which is a technique that discloses the cognitive structure, provides an opportunity to evaluate the structure of connections between the creations of knowledge within the minds of individuals. This also includes the question as to whether these connections are considered logical or not. The goal of this study is to examine the cognitive structures of primary school Turkish pre-service teachers in regards to the concept of light. This also happens to be one of the basic concepts of science, by means of the word association test. The sample group within this qualitative research study was comprised of 35 pre-service teachers, who were all in the process of studying at the 3rd grade in the Department of Primary Education. The sentences formed by each of the pre-service teachers in regards to the concept of light were evaluated in terms of the categories developed by Ozata-Yucel & Ozkan (2015). Whilst the pre-service teachers generally associated the concept of light to the concepts of the sun, stars, light bulb, illumination, energy, light refraction, velocity of light, artificial light source, linear road, electricity, lamp and the moon, it was determined that the concept of light was to be related to the individual source and nature of light.