The current research was qualitative and it was done with the aim of investigating the effect of misunderstandings of chemistry concepts on the teaching of second cycle secondary school biology subjects. The research sample was selected using simple random sampling. The research population consisted of all experimental science 12th grade female students in Javādābād district of Tehran province in the academic year of 1400-1401. A sample of 37 students from two schools was selected to answer the questions of the questionnaire. The questionnaire included 10 biology questions related to the chemistry concepts which was designed based on the information obtained from the interview with biology and chemistry teachers.  In this interview, the chemistry teachers pointed out the concepts in which the students often have misunderstandings and biology teachers determined the topics that are closely related to the chemistry concepts and a misunderstanding in them disrupts the education. After checking the students' answers, they were asked in an interview to explain their answers to reveal their understanding and perception and the reason behind forming wrong perception in their minds. Then, the students' common misunderstandings and the reasons behind them were investigated. The results showed that the main cause of students' misunderstanding in some biology topics is the misunderstanding in their prerequisite chemistry concepts. Finally, solutions were provided to resolve these misunderstandings.