This study was conducted to explore a comprehensive belief system model of pre-service science teachers' (PSTs') beliefs and to examine the reasons why and how these beliefs are in/consistent with each other. A sequential explanatory research design guided the study, with a quantitative approach being followed by a qualitative one. Participating in the quantitative research were 955 PSTs. The results of a structural equation modeling analysis of the dataset indicated that PSTs' depressive beliefs were related to their epistemological beliefs and that these latter beliefs predicted their teaching-learning conceptions. Twelve PSTs participated in a follow-up research that employed a multiple case research design. Results, at this step, indicated that there was a relationship between a PST's beliefs and experiences. Furthermore, if any inconsistencies between experiences and peripheral beliefs existed, the relationship was biased toward experiences. Therefore, the experience-biased calibration determined that central beliefs have a greater influence on peripheral beliefs than vice versa. Given these results, certain implications are presented.