The purpose of study was to investigate the effect of teaching Physics using Needham\'s constructivist Model in developing the critical thinking skills of tenth -grade students in Jordan. A critical thinking test consisting of (25) items, was applied over purposively sample consisting of (53) students in Mafraq -Jordan schools, randomly distributed into two groups: (1) as an experimental group which contains (27) students who were taught by the Needham\'s constructivist Model, (2) as a control group which contains (26) students. The results showed that there were statistically significant differences between the averages of the two groups in critical thinking skills as a whole in favor of the experimental group. The study recommended the use of Needham\'s constructivist Model in teaching physics.