Translation ability requires many language skills to produce an accurate and complete text; however, one important skill, critical reading in the research, has been neglected. This research, therefore, employed the explanatory sequential mixed method to investigate the differences in Thai-English translation ability between students with a high level of critical reading skill and students with a low level of critical reading skill, and to examine the relationship between translation ability and critical reading skill. Moreover, translation error analysis, with four main aspects, pragmatic, syntactic, semantic, and miscellaneous errors, was also conducted to explore the dominant translation errors committed by both groups of students. To this end, the participants of the study were 60 English major students from a Thai university. The results of the study showed that there was a significant difference in Thai-English translation ability between the students with a high level of critical reading skill and the students with a low level of critical reading skill, and a significant correlation between translation ability and critical reading skill. In the translation error analysis, the semantic aspect, particularly the wrong use of words, was found to be the most frequent error committed by both groups of students.