The present study aimed to investigate the effectiveness of a training program on the development of critical thinking among Saudis students enrolled in undergraduate studies. It which included a system of critical thinking skills, namely: deductive reasoning, drawing inferences, recognizing assumptions, argument evaluation and logical interpretation. Forty undergraduate Saudi students participated in this study. All were withdrawn from the population of the Psychology department at King Saud University. Their ages ranged between 18 and 23 years with an average age of 21.70 and a standard deviation of 0.88. All were randomly assigned to two equally numbered experimental and control groups. A training program was constructed to develop the critical thinking skills among the students. Those in the experimental group were trained on this program during 8 sessions, 2 sessions per a weak with 2-3 hours in each session. A critical thinking scale prepared by the National Center for Youth Studies (2014) was used to ensure program effectiveness. Results revealed the effectiveness of the training program on the development of critical thinking skills of the study sample in the general ability of critical thinking as well as in the capacity of its constituents
