This study aims to identify analyses and describe errors committed in passive voice forms and structure in Iraqi theses and dissertation in field biology. Ten random samples theses and dissertation from different colleges in field biology were examined and analyzed also investigated the frequency of errors in each chapter in theses and dissertation. The findings of this study reveal the followings: • There are a variation in using passive voice in Ph.D. dissertations and M.Sc. theses in all chapters. • The fourth chapter (Methods and Materials) contains the highest percentage of errors in passive voice forms. • There is a significant difference in the errors committed between dissertations theses chapters. • Using passive voice verbs represents the prominent feature in all dissertations and theses. • Many theses/dissertations showed lack auxiliary verbs. • There is a difference in the percentage of distribution of errors committed among all chapters whether in PhD. dissertations or M.Sc. theses.