This study aimed to investigate the effectiveness of training program in reflective teaching in the development of teaching performance and reflective thinking among science teachers in the second cycle of basic education. The sample consisted of (17) science female teachers taught classes (5-10) at basic education at the Governorate of Aldakliya Region. To achieve the study aims, the researcher has constructed a training manualin reflective teaching. In addition, an instrument of the level of reflective thinking was designed. In addition the classroom observation checklist which is used by Ministry of Education was used. The validity of both training guide and the level of reflective thinking scale were checked through a panel of specialized judges, where the reliability found to be (0.89) for the level of reflective thinking scale using Alfa Cronbach for internal consistency and (0.82) for the reliability of the two observer of the classroom observation checklist by using person correlation. The results of the study showed that there were significant differences at (a=0.05) between the means of science teacher's scores in pre and post classroom observation checklist in favor of posttest. In addition, the results showed that there were significant differences at (a=0.05) between the means of science teacher's scores in pre and post the level of reflective thinking scale in favor of posttest. Accordingly, the researcher recommends tailoring an in-service training program in reflective teaching for science teacher in order to enhance their performance. The researcher also suggested some further relevant studies.