The study aimed to evaluate the effectiveness of the English language experts program at the Specialized Institute Professional training for Teachers in the Sultanate of Oman according to the Gusky’s model. To achieve the goal of the study, the researcher used the sequential explanatory design, employing three tools to collect data, which are: The questionnaire included 36 items distributed over five dimensions according to the Guski’s model (the level of teachers’ satisfaction, the level of new knowledge and skills, the level of support , the level of teachers’ application of the training material, and the level of influence on students’ learning outcomes). This questionnaire was applied to 171 male and female teachers from various governorates. The second instrument was also a questionnaire intended for educational supervisors to identify the extent of influence the teachers had on the learning outcomes of their students, from the point of view of 31 educational supervisors of these teachers who graduated from the specialized institute and their headmasters to explain the results obtained from the questionnaire. The third instrument was a semi-structured interview that was applied to 10 graduates from the Specialized Institute in the English Language Experts Program to measure the impact of the training program on them. The results of the study indicated that the opinions of male and female graduate teachers from the English Language Experts Program who answered the questionnaire were very high in all five dimensions of the Gusky model. The results of the questionnaire answered by the educational supervisors also indicated that the impact of teachers on the learning outcomes of their students was also very high. With regard to the differences between males and females, ‌ي the results showed that there were no statistically significant differences between male and female teachers with respect to all the dimensions the Guski’s model, while there were statistically significant differences with regard to the academic qualification variable in favor of master’s degree holders in the level of teacher satisfaction dimension only. The results also indicated that there were statistically significant differences with respect to the years of experience variable in favor of the more experienced teachers. The study concluded with a set of recommendations and suggestions based on the results obtained from the results of the study.