Purpose: This study investigated common errors and misconceptions made by some pre-service mathematics teachers of the St. Louis College of Education in Ghana about operations on integers. Errors associated with the misconceptions were also explored. Methodology: The study employed mixed-method and sequential explanatory design, Diagnostic test instruments were designed and administered to sixty (60) pre-service mathematics teachers who offer specialized programmes in early grade (EG) and upper primary (UP). Findings: The study identified common errors made by pre-service mathematics teachers as interpretation of the inequality symbols  and ,  addition and subtraction of integers, multiplication and division of integers, problem-solving (word problems). The study also found introduction concept of operations on integers, interpretation of absolute value of integers, problems involving change in the order of operation of integers as common errors made by pre-service mathematics teachers. Furthermore, the study found problems involving more than one operation, over-reliance on calculator usage and rote-learning, and inability to formulate word problems as mathematics problem. Conclusion: The study conclude that deficiency in the language was the course of their inability to solve word problems. Recommendations: The study recommends that when solving word problems involving integers, pre-service mathematics teachers should take read over the problem thoroughly to understand the problem properly. Also, during teaching and learning of mathematics, particularly operations on integers, much attention must be given to helping learners to translate normal language into mathematics language to overcome language deficiency. The study suggest that similar study could be done in other Colleges of Education and institutions to expound the findings.