The purpose of this study was to investigate (1) the relationship between critical thinking skills (CTS) and critical thinking dispositions (CTD), and (2) the effectiveness of different levels of instructional strategy (asynchronous online discussions (AODs), CTS instruction via AODs, and CTS instruction with CTD cultivation via AODs) in improving students' CTS and CTD. A pretest and posttest quasi-experimental design was employed to achieve this purpose. The participants in this study were 220 students enrolled in a general education course at a large university in Taiwan. The findings of this study were as follows: (1) the overall relationship between CTS and CTD was positive. However, further analysis of the relationship between the different levels of CTS and CTD showed that only the students with high CTS and medium CTD showed a significant correlation; (2) the enhancement in CTS reinforced CTD, but the improvement in CTD did not increase the level of CTS. In addition, it is recommended that to improve the CTS and CTD of all students (including the students with a high level of CTS), the instructional strategy, CTS instruction with CTD cultivation, be employed.