The aim of this study is to examine pre-service mathematics teachers' conceptual structures about "geometry". Qualitative research methodology has been adopted in the study. The data of the study is obtained from mathematics teacher candidates who have been students at the faculties of education of an Anatolian university in the academic year of 2015-2016. The free word association test was used to collect the data. The "geometry" stimulus word is presented to participants by the word association test. A total of 65 response words obtained from the test have been arranged in frequency tables. The answer words were divided into 13 categories with the help of content analysis. Considering the frequencies and categories of answer words, a network of concepts has been developed that outlines the conceptual structures of pre-service mathematics teacher about "geometry". At the end of the research, the answer words with the highest frequency of the mathematics teacher candidates related to the "geometry" stimulus word are triangle, angle, area, polygon, etc. and the categories of answer words are triangle, quadrilateral/polygon, basic concepts of geometry, measurement, etc.