The primary purpose of this study is to investigate the level of self-efficacy beliefs in speaking skills amongst Level Six English as a Foreign Language (EFL) students at the Center for Preparatory Studies (CPS) at Sultan Qaboos University (SQU). It also explores the differences in beliefs in the light of gender. Amongst Bandura's (1997) four sources of self-efficacy beliefs (i.e. mastery experience, vicarious experience, social persuasion, and psychological and emotional arousal), the study explores the most predictable sources of students' speaking self-efficacy beliefs. Finally, it aims to investigate the relationship between these beliefs and students' speaking skills performance. To this end, the study; therefore, addresses the following research questions: 1. What is the level of speaking self-efficacy beliefs of CPS EFL Level Six students at SQU? 2. Are there any significant differences in the speaking self-efficacy beliefs between male and female CPS EFL Level Şix students? 3. Considering Bandura's four sources of efficacy beliefs, which of the sources is the strongest predictor for students' speaking self-efficacy? 4. Is there any significant correlation between students' speaking self-efficacy beliefs and their speaking achievement? Two instruments were used to answer the research questions: the first instrument is a two-part scale. The first part of the scale is the speaking self-efficacy scale, which was developed by the researcher based on a literature review and previous self-efficacy scales. The second part is the speaking skill self-efficacy source scale, which was adopted from Pajares and Usher (2009), and Choy and Loo (2013). The second instrument was the total collected scores of students' speaking achievement, which were obtained from the CPS teachers. The collected data were treated using appropriate statistical techniques consisting mainly of t-test, correlation coefficient, and multiple linear regression. The reliability coefficients of the first and second scales were .94 and .91, respectively, The sample of this study was EFL humanities students at SQU, who were enrolled at Level Six of the language programme at the CPS (2018-2019). It consisted of 121 male and female students, The findings of the study can be summarized as follows: 1. EFL humanities Level Six students hold moderate levels of speaking self-efficacy beliefs. 2. No statistically significant difference was found between male and female students in terms of their speaking efficacy beliefs. 3. The experience of mastery was found to be the strongest predictor of students' speaking efficacy beliefs. 4. No statistically significant correlation was found between students levels of speaking efficacy beliefs and their speaking achievements. In the light of these research findings, certain implications and recommendations for further research are outlined.