This paper investigates the link between critical thinking (CT) skills and mathematics scores among engineering students by analyzing two batches of students. The study assessed CT skills through online discussion forum (DF) postings using the CAIS model, assigning weighted CT scores to each student. Mathematical achievement was measured through final exam scores, with initial mathematics ability assessed via a preliminary test. Results showed a significant linear relationship between CT and mathematical achievement, although the relationship between initial mathematics ability and CT scores was significant for only one batch. The study concludes that fostering CT skills can enhance mathematical achievement.