Background: In the last decade, the world has been facing global challenges of climate change as the climate has worsened significantly. Excessive consumption has been identified as one of the biggest contributors to the climate change where people purchase more products than what meets the basic needs. The excessive consumption of products has been prominent in the fashion industry, where female consumers generally purchase more clothes than men. Today, the fashion industry is dominated by fast fashion, where consumers purchase more clothes with a shorter life span. Thus, the fashion waste increases, leaving serious environmental effects. Sweden is said to be one of the greenest countries in the world but is still one of the countries with the highest levels of consumption globally. The private consumption is high in Sweden and one of the biggest consumer markets that have a negative effect on the environment is the fashion industry. As a result, sustainable fashion consumption is becoming more important.   Purpose: The purpose of this study is to explore the sustainable behavior of Swedish female consumers and later understand how different factors is affecting the IB gap in sustainable (secondhand) fashion consumption.   Method: To be able to achieve the purpose of this exploratory study, a qualitative research strategy was applied. The empirical data was collected through in-depth interviews held with Swedish female consumers with intentions to purchase secondhand fashion, which later was interpreted and analyzed through an abductive approach, incorporating a thematic analysis.   Conclusion: The results of this study showed that the behavior of intenders can be characterized by sustainable intentions that do not translate into behavior. Further, the behavior can be characterized by a weak social support system (barrier), poor availability (barrier), low task- and maintenance self-efficacy, high recovery self-efficacy, and no planning. In addition, the results of this study showed that the behavior of actors can be characterized by sustainable intentions and sustainable behavior. Further, the behavior can be characterized by a strong social support system, good availability, high task- and recovery self-efficacy, medium to high maintenance self-efficacy, and planning. The comparison between intenders and actors showed that the perceived barriers for intenders was contributing factors to the IB gap together with their low task- and maintenance self-efficacy through their most likely negative effect on intenders planning. Intenders lack of planning was shown to serve as a negative mediator between intention and behavior, which thereby contributes to the IB gap. While the recovery self-efficacy was high for both intenders and actors, actors has recovery self-efficacy for the desired behavior of purchasing secondhand on a regular basis, while intenders does not.