The emergence of social media has increased the speed and scope of disseminating false information. Combating misinformation has, therefore, become one of the most pressing issues in countries around the world, including Taiwan. Among various means of prevention, the skills of evaluating online content are especially important, also known as “civic online reasoning” (COR). However, most studies in this field focused on the role of workshops in facilitating COR and did not examine the utility of it. This study explores other factors that contribute to the development of COR, with a particular emphasis on the effect of media use and social capital. The current study is also one of very few research that investigates the “fact-checking before sharing” behavior. Based on the 2020 Taiwan Communication Survey, the results of the counterfactual analysis show a positive relationship between COR and fact-checking before sharing. The structural equation model indicates that COR is indirectly associated with fact-checking before sharing through the perceived impact of false information. In addition, people who frequently consume online news, engage with online opinion leaders, and have more bridging social capital also have higher levels of COR.