The objective of this study is to examine the effect of the Test-Teach-Test strategy on developing the achievement of Iraqi EFL learners. The TTT strategy is an action-based approach of testing learners' existing knowledge and providing specific instruction, then re-testing learners' improvement. This study aims to explore whether or not the strategy can guarantee significant improvement in students' language competence, as an indicator through pre- and post-achievement tests. Two groups of Iraqi EFL students participated in the experiment: a control group, which was taught using the conventional way, and an experimental group, which was taught using the TTT approach. Pretests were administered prior to the teaching period in order to allow the participants to begin on an equal footing, and posttests were administered after the intervention in both the control and experimental groups to measure the impact of the teaching method. Statistical comparison between the posttest scores using independent samples t-tests indicated improvement much higher in the control group when compared to the experimental group. The results confirm that the TTT strategy has a positive and quantifiable impact on the success of Iraqi EFL learners. The results show that task-based teaching practices, i.e., the TTT strategy, are better than conventional ones in developing language abilities. The research adds to the evidence that interactive and student-focused teaching practices should be implemented in language learning environments. Follow-up studies can study the long-term impact of the TTT approach and how it impacts certain of the language competences namely, speaking, listening, reading, and writing.