In particular, it is of great importance that teacher candidates are trained to develop awareness of ecology and to protect ecological systems. Because they are the ones who will be educate future generations. Ecology is generally a conceptual field. In this study, it was aimed to determine the conceptual structures related to ecology of science teacher candidates at cognitive level. The study is a qualitative research carried out by the screening model. The study was carried out with the participation of 127 candidates' science teachers. In this study, a word association test (WAT) was used to determine the cognitive structures of science teacher candidates related to "ecology". Content analysis and descriptive analysis methods were used in the analysis of data. In this data, the frequency table has been formed. Based on the frequency tables prepared according to teacher candidates' responses to WAT, concept networks related to ecology have been established. In the preparation of concept networks, cut point technique was used. When we look at the frequency table, it was observed that the key words that teacher candidates associate most with ecology are living places, functional properties of ecology and biotic factors of ecosystems in ecology. The sentences of teacher candidates related to ecology are selected and categorized according to the concepts they contain. When the sentences of teacher candidates related to ecology are examined, it is seen that correct descriptions are found but in many of them there is incomplete information or concept confusion.