Flipped Instruction is overemphasized in recent years that has a significant impact in language education. In this context, the current research investigates the effects of Flipped Instruction on pre-service English language teachers' speaking skills development. The research covers subskills of speaking skills. In this study quantitative data were collected. The data were collected to investigate whether Flipped instruction based syllabus which was designed specifically for the research is effective to develop participants' speaking skills. The syllabus is called as OCS1FS which stands for flipped syllabus for the course. Pre-test and post-tests were administered to both experimental group and control group with the aim of collecting data. The data were analysed through SPSS. The results show that there is statistically significant difference at, 000 (Sig > 0.05) levels between groups at the end of an eight-week treatment process. It is found that experimental group students developed significantly in terms of fluency, coherence, lexical resource, grammar, pronunciation and accuracy skills.