Inconsistent leadership refers to a pattern where a leader's actions, decisions, and interactions with employees shift unpredictably, making it difficult for employees to understand their leader's expectations. This inconsistency fosters an environment of ambiguity, prompting behaviors that deviate from the organization's core values. Drawing on Uncertainty Reduction Theory, we propose that employees, when faced with inconsistent leadership, resort to deviant behaviors such as unethical pro-organizational behaviors and coworker undermining to gain advantage in such a competitive environment and reduce the uncertainty stemming from that environment. We also propose that this relationship occurs because employees adopt competitive and aggressive behaviors, characteristic of masculinity contest cultures. To empirically test these relationships, we conducted a time-lagged study across three waves, gathering data from 300 employees across various organizations. Our findings highlight that inconsistent leadership indeed promotes both unethical actions intended to benefit the organization and behaviors that undermine colleagues to maintain or enhance their status. Additionally, we identify perceptions of masculinity contest cultures as a key mediator in these relationships. Our study not only deepens the understanding of how inconsistent leadership fosters deviant behaviors in the workplace but also offers actionable insights for organizations aiming to reduce these negative outcomes. Specifically, we show that inconsistent leadership, by exposing employees to unpredictability, induces a climate of hypercompetition that drives individuals to engage in self-preserving behaviors misaligned with organizational ethics. Our research further extends the theoretical discourse on the nomological network of inconsistent leadership, offering a nuanced view of how uncertainty disrupts ethical climates and interpersonal relationships within organizations.