This study was conducted to examine the effect of in-service training of computer science teachers in Scratch language using an electronic learning platform on acquiring programming skills and attitudes towards teaching programming. The sample of this study consisted of 40 middle school computer science teachers. They were assigned into two groups; 20 teachers were in the control group and 20 teachers in the experimental group. The study tools consist of an achievement test in Scratch programming language and a measure of attitudes toward programming instruction. After the experimental treatment at the end of the second semester, the teachers were examined and the results showed that there were statistically significant differences between the achievement test mean scores in favor of the experimental group that trained using an electronic training platform. The results also showed a positive effect on attitudes toward teaching programming for the experimental group.