While numerous people use social mobile applications, ads within these apps are often avoided. Although the significance of prior negative experience and personality traits in impacting consumers’ perceptions and behaviors has been acknowledged, limited research has explored their influence on ad perceptions and avoidance. This study aims to examine the effects of prior negative experience and personality traits on ad perceptions and ad avoidance of Generation Y (Gen Y) and Generation Z (Gen Z) within two prominent mobile social apps: WeChat and TikTok. An online survey was used to gather data from 353 Chinese Gen Y and Gen Zers who were active users of WeChat and TikTok. Findings from several regression analyses show that prior negative experience is an essential determinant of ad avoidance, influencing not just directly but indirectly by diminishing perceived ad personalization and intensifying perceived goal impediment and ad clutter. Personality traits also significantly affect ad avoidance, with conscientiousness exerting a positive effect, whereas agreeableness has a negative impact. Notably, agreeableness, emotional stability, and openness to experience moderate the associations between ad perceptions and avoidance. Intriguingly, the effects of these factors are platform-specific, with WeChat’s main factor for ad avoidance being erceived goal impediment and TikTok’s main factor being ad clutter. Based on these findings, the theoretical and practical implications are discussed.