This study explored the relationships among preservice teachers’ mathematics and science teaching efficacy beliefs, their pedagogical content knowledge (PCK) and their domain knowledge (DK). It was found that participants’ PCK and efficacy beliefs correlate to a high degree and influence each other. Furthermore, the results indicated that participants’ mathematics and science DK did not predict their teaching efficacy beliefs, however, their mathematics and science overall PCK score predicted participants’ efficacy beliefs, more exactly, their outcome expectancies. Furthermore, the findings show that elementary preservice teachers’ previous efficacy beliefs are more likely to predict their future efficacy beliefs than their mastery of DK and PCK.