This study aimed to identify the effect of the strategy (think, pair, share) on the development of mathematical thinking and achievement of students in the seventh grade in the Sultanate of Oman. So this study had been applied to the students of grade seven in Majed Bin Kamis school (5-10). The researcher followed the semi experimental approach, which included the choice of experimental design with the experimental and control groups, through (54) Students were divided into equal groups. The experimental group studied the strategy (think, pair, share) while the control group studied using the normal method. The results showed a statistically significant difference at the level of (α = 0.05) between the average scores of the experimental group and the average score of the control group students in the test of mathematical thinking and the achievement test for the experimental group. A number of recommendations and proposals for future studies were formulated following the results of the Current study adapting the (Think-Pair-Share) strategy to improve student's mathematical thinking and achievement and apply it in the various educational fields.