The study investigated the reflective dairies and epistemological beliefs of sophomore elementary preservice teachers (PTs) who were taking a "science laboratory" course. Twenty volunteers were participated in the study. The data were collected through the reflective dairies and open-ended questions about their epistemological beliefs. The data obtained from the reflective diaries were evaluated using descriptive analysis. The participant answered the open-ended questions twice, before and after the intervention. Chi-square analysis was used to find out whether there was an interaction between the reflective diaries and the epistemological beliefs of the PTs. The study has shown that the scores given for the reflective diary improved every week. The study also found that epistemological beliefs developed in all dimensions except for the certain knowledge dimension. In addition, the results of this study may suggest that there is a positive interaction between the participants' reflective diaries and the dimensions of their epistemological beliefs.