This study aimed to investigate the impact of the using( K.W.L ) teaching strategy on science achievement and metacognitive skills of ninth grade students in the Sultanate of Oman. The sample of the study consists of (62)students of grade nine in Abu Bakr Al Razi basic school in Al sharqya south region. The sample was divided into two groups, the experimental group consists of (32) students who were taught by (K.W.L ) strategy and the controlled group consists of (30) male students who were taught by the conventional method. The study lasted for six weeks in the second semester of 2013/2014 academic year. To achieve the goal of the study, a test was constructed on science achievement and was verified by arbitrators and the co-efficient of reliability was (0.79) which is accepted for the study. The researcher also used one of the tests prepared for measuring metacognitive skills for grade nine students and the co-efficient of reliability was (0.82). The results of the study indicated that there were statistically significant differences at level (a=0.05) between the average scores of experimental group students and the controlled group students in the science achievement post test favouring the students in the experimental group. Also the results indicated that there were statistically significant differences at level (a=0.05)between average scores of the experimental group students and the controlled group students in the metacognitive skills post test favouring the experimental group. Based on the results mentioned above, the study recommends to encourage teachers to use( K.W.L ) strategy in teaching and to emphasise the importance of developing metacognitive skills. The study also recommends conducting workshops for teachers and supervisors to acquaint them with( K.W.L) strategy and how to practise and implement it in teaching science and conducting more studies on the effect of. using(K.W.L) strategy on other variables using different school levels.