Self-efficacy in language learning have been attracting interest recently. The construct is said to be a reliable predictor of language performance. This study is aimed at explaining the relationship of self-efficacy and speaking proficiency of male and females. It was administered to investigate whether self-efficacy correlates to speaking proficiency. In addition, the study seeks answer regarding the difference of self-efficacy and speaking proficiency of male and female students who were taking ESP. The study was a quantitative research with ex-post facto design. Pearson Product Moment Correlation Coefficient and t-test were used to analyze the data collected from 92 subjects who were Diploma IV students. There were 17 females and 75 male students that were selected based on purposive sampling technique. They were second grade students which were in the third semester. The result of analysis presented that self-efficacy had significant correlation with speaking proficiency. on the other hand, self-efficacy of males and females were not significantly difference. The score of self-efficacy between males and females were only slightly different and categorized as medium. Furthermore, gender did not influence speaking as both males and females had medium level speaking proficiency. It can be wrapped up that self-efficacy predicts speaking proficiency, nevertheless gender does not link to self-efficacy and speaking.