The purpose of this study was to investigate effect of training in conditions of high psychological pressure on the performance and learning of swimming in children and adolescents. The method of the current research was quasi experimental with a pre- post-test design. The study sample was 30 female teenage novice swimmers (Average age: 13.2±6.6) and 30 child swimmers (Average age: 9.2±2.5) who were selected from among all convenience swimming pool registrants in District 2 of Tehran. Each of the age groups of children and teenagers were randomly divided into two groups of control (n=15) and experimental (n=15). The data of the acquisition, retention and transfer tests were collected using the checklists for evaluating the movement components of breaststroke skills that were completed by the trainers. The results of 2 (age)* 2 (training) ANCOVA showed that training under high psychological pressure significantly reduces performance during the acquisition period and significantly improves learning based on retention and transfer tests. Also, the main effect of age group was significant and the average performance, learning based on retention and transfer tests of teenagers were higher than children. Finally, the interaction of training and age on swimming performance and learning was not significant. According to the results of this research, it seems that based on the hypothesis of the specificity of training, in order to achieve better results in competitions, coaches need to teach swimming breaststroke skills under the psychological pressure associated with competitions.