T.H.I.N.K. is an educational a strategy designed to enhance critical thinking and collaborative problem-solving skills among students. This strategy is particularly effective in language learning contexts, where collaboration and communication are essential. T.H.I.N.K. stands for True, Helpful, Inspiring, Necessary and Kind. This study aims at finding out the effect of T.H.I.N.K strategy on Iraqi EFL pupil`s achievement. Finding out the effect of T.H.I.N.K strategy on improving EFL pupil`s post achievement test. The study includes the following hypothesis, There is no statistically significant differences between the mean scores of the experimental group which is taught by T.H.I.N.K strategy and the control group which is taught by the traditional method in the post achievement test.There is no statistically significant differences between the mean score of the experimental group in pre- posttest. The research population consists of 72 students from fifth preparatory schools in city, with a sample of 52, for each group 26 students randomly selected from the fifth preparatory class at Al-Bojwari secondary School for boys at Salah AL-Din governorate / in Baji City. To ensure comparability, both groups are matched on parental educational level, age, previous English scores, and pre-test results. The study employs a post-test consisting of six questions assessing four skills. The data collected from these instrument are analysed statistically using the T-test for independent and paired samples. The findings indicate that the T.H.I.N.K strategy positively influences the experimental group's English learning outcomes compared to the control group. The study end with some conclusions with recommendations for future research to further explore the benefits of the T.H.I.N.K strategy in an educational setting.