The coronavirus disease 2019 outbreak has severely impacted the global economy, particularly the tourism industry. Lockdowns and epidemic prevention measures imposed in many countries have restricted the range and methods of travel. However, since many people still need to travel, they may change their initial plans through substitution. This study examined the travel substitution behaviors of Taiwanese citizens during the pandemic based on the theory of planned behavior. By including an additional perceived risk variable, we expanded the theory of planned behavior model to analyze the association between the perceived risk level and changes in travel behaviors during the pandemic and the possible travel substitutes adopted by visitors for dining, accommodation, transportation, sightseeing, shopping, and entertainment. We used a mixed-method approach, conducting in-depth qualitative interviews to examine the interviewees’ potential travel substitution behaviors during the pandemic and then developing and administering a pre-test questionnaire based on the interview results. Then, we used convenience sampling to administer 580 online questionnaires to financially capable Taiwanese citizens aged ≥18 years. This study successfully developed an extended TPB model to examine the travel intentions of Taiwanese citizens during the pandemic. The results indicate that visitors have more intentions to travel when they have substitutes in the post-pandemic era. Moreover, the explanatory power of perceived behavioral control on travel-related behavioral intentions was stronger than attitudes and subjective norms. Our results are expected to provide a reference for tourism operators to suitably adjust their business models during an uncertain time.