Our decisions and attitudes are profoundly shaped by social influence. Studies showed that individuals often align their behaviors with peers under uncertainty, a phenomenon known as the "social contagion" effect. Yet it remains unclear how the social contagion effect in behavioral preferences is influenced by disparate others (e.g., conservative vs. adventurous) and modulated by different forms of uncertainty (e.g., risk vs. ambiguity). To address these questions, we conducted two independent experiments (N1 = 40 and N2 = 56) to investigate and directly compare the social contagion effect of risk and ambiguity preferences. We found that participants shifted both their risk and ambiguity preferences towards observees after observing their decisions. Intriguingly, participants aligned their risk preferences more toward risk-averse than risk-seeking observees, revealing an asymmetry in risk preference update. In contrast, we did not find reliable evidence for an asymmetric social contagion effect in ambiguity preference. Results from both experiments were fully replicated in a preregistered replication study (N1 = 61 and N2 = 62). Together, our findings highlight distinct patterns of social influence on risk and ambiguity preferences, implicating the subtle interplay between social information processing and decision-making under uncertainty.