This study aimed to investigate science teachers' beliefs about teaching in the vision of "constructivism theory", and the extent in which these beliefs are effected by: gender, and teaching experience. The study also aimed to identify the range of using the applications of "constructive theory" by science teacher and to explore the relation between these beliefs and the practitioner. To gather the data, two instruments were used: beliefs scale which consists of 31 items, and the observation instrument which also consists of 31 items. The sample of the study consisted of 108 male and female teachers of whom the beliefs' scale was administered. The observation instrument was administered on 39 teachers from the same sample. The results of the study showed that the mean score of science teachers' beliefs about teaching in the light of "constructivism theory" is (3.49), which means that it is unaligned. The results also showed that there is a fluctuation in the mean score at the same domain which indicates that the principle of the "constructivism theory" was not properly deep-rooted at the teachers' minds. Moreover, there were statistically significant differences between male and female teachers' beliefs about teaching in the light of "constructivism theory", which can be attributed to female in teaching and classroom environment domains and for the whole instrument. The results showed that there was no significant differences were found between the short, medium and long teaching experience. In addition, the results showed that science teacher rarely applicate the "constructivism theory" principles, and there is no statistically significant relation between science teachers' beliefs about teaching in the light of "constructivism theory" and their classroom practice. The study has concluded to some recommendations in light of what the findings covered, for instance: Include the applications of constructivism in the programs of teachers training through their duty and so the supervisors. This is to make it more easy to take up and then to applicate; Look toward teachers preparations, especially the linking between theoretical instructions and the teaching methods that arise from.