The aim of this study was to recognize the effect of a proposed cooperative learning strategy based unit on developing one of life skills for the students of secondary stage. The study included one experimental group. The tools of the study included a list of life skills needed to be developed, an achievement test, a teacher' s guide besides preparing a proposed educational unit.  Thirty   Students in their second year of secondary school were chosen for the study's experimental group. This experimental group was tested using pre – post achievement test   before and after being exposed to cooperative learning strategy treatment. The experiment was conducted for two months during the first term of 2017-2018 school year at Alafai secondary school for girls at Arish city. The experimental design consisted of one group of 30 students of second grade. Scientific Department Results of the study revealed significant statistical differences between the pre –test and post test of achievement test. It was concluded that cooperative learning strategy to secondary school students was effective on developing their life skills.