Since teachers are known to be models in the classroom, mastery of the course they teach and a good English proficiency should be a few of the qualities that should be considered. This present study attempts to identify, classify, and analyze the sentence-level writing errors found in the compositions of fifty (50) selected probationary faculty members in one of the universities in Mindanao, Philippines. The instrument used in the study was the participants’ composition in English. Fifty compositions were subjected to error identification, classification, and analysis. Findings revealed that syntactical errors were found common in the participants’ compositions. Other errors found were lexical, morphological, and mechanical. The results showed that the probationary faculty members really need a refresher course on the basics of the language for the enhancement of their language ability. The implication of this study is for the school administrators, deans, and department heads to look into the English proficiency of their faculty members and design a language enhancement training program to address the problem.