The aim of the present study is to determine the elementary pre-service mathematics teachers' understanding on solids. For this purpose, pre-service teachers' definitions and drawings of these objects were examined. Qualitative research method was used. A written questionnaire consisting of sixteen open- ended and multiple-choice questions was conducted with 127 elementary pre-service mathematics teachers chosen by convenience sample which is one of non-random sampling method. The collected qualitative data were analyzed by both descriptive and content analysis. The results revealed that pre-service teachers made insufficient connections among cylinder, prism, cone and pyramid. So, it can be said that their understanding about solids was weak and procedural.