As short-form video (SFV) apps like TikTok continue to gain popularity and deliver personalized content to users, they raised concern about the potential for building information cocoon and reinforcing prejudice about certain social group. Our study explores the factors influencing sexism among users of SFV platforms, focusing on how content diversity, selective exposure, and susceptibility to persuasion shape gender attitudes. The research was conducted by a questionnaire survey, based on existing theories of ambivalent sexism and information cocoons, highlighting how homogeneity in content can reinforce sexist attitudes. Our findings suggest that lower diversity in content exposure increases sexism towards both genders, reinforcing existing stereotypes. Additionally, users with lower susceptibility to persuasion and those more inclined to selective exposure are more likely to develop stronger sexist attitudes. In particular, all participants reported perceiving an increase in prejudice towards both genders after engaging with SFV content. These results provide insights into how SFV apps propagate biased content and influence gender attitudes, emphasizing the need for content diversity and media literacy to counteract biases and promote gender equality. This research contributes to the growing body of literature on digital media’s role in shaping social attitudes, offering practical implications for reducing gender prejudice in online spaces.