The purpose of this research is to examine preschool and first grade teachers’ opinions on the effects of school readiness to classroom management. The participants of this research consisted of the 18 preschool and 22 first grade teachers who work at public and private schools in the cities of Konya, Ankara and Kayseri in Turkey. Phenomenological research design is used in this qualitative study. In order to identify the opinions of the preschool and first grade teachers on the effects of school readiness to classroom management, an interview form comprised of open ended questions developed by the researchers was used. The data is gathered from the teachers’ answers given to the structurally prepared questions and the collected data is analysed through content analysis method. The result of the research shows that both the preschool and first grade teacher groups expressed that level of readiness has an impact on classroom management. The teachers in both groups have stated that it is observed learning difficulty in children with low level of readiness and boredom and impatience in children with higher level of readiness. At the end of this research the necessary suggestions were given according to the obtained findings.