Professional development of teachers has key role in raising their self-efficacy and instructional quality. Teachersare trained before they adopt teaching as a profession in degree or diploma courses with the name of pre-service teacher training. They are constantly trained during their job with the name of in-service teacher training. The objective of its conduction is to polish teachers? skills, enhance performance and increase self-efficacy for obtaining luminous results in the classrooms. The study at hand was intended to unearth the impact of in-service teacher training on secondary school teachers? self-efficacy about teaching skills in the context of Balochistan. The study was quantitative in nature and the design adopted for the research was causal comparative. The questionnaire used for the collection of data was OSTES (Ohio State Teacher Efficacy Scale) which was initially developed by Tschannen-Moranand Hoy (2001). The questionnaire had twenty-four statements divided into three sub factors of self-efficacy. Convenient sampling technique was used and 107 respondents who were trainees at PITE (Provincial Institute for Teacher Education) Balochistan were selected for the study purpose. They were given the research questionnaire before they attended the training and after they attended the training. The mean score was then compared to see whether the in-service teacher training impacted the self-efficacy of targeted secondary school teachers of Balochistan. The data was analyzed by SPSS using independent sample t-test, dependent t-test and ANOVA. The study revealed that in-service teacher training has statistically significant impact on secondary school teachers? self-efficacy about teaching skills. Their gain score on self-efficacy scale was significantly increased based on the evaluation of pre training responses? differences from post training ones. However, gender, professional qualification, length of teaching experience and teaching grade level did not show any noteworthy difference on self-efficacy. The respondents had greatly benefited of in-service teacher training and their beliefs were increased about involving students in learning activities, using effective teaching methods and managing classroom as per the learning needs. Findings of this research invite for further researches regarding in-service teacher training through different dimensions to investigate for further improvement in the education of Balochistan.