Anecdotally, attributions that others are biased pervade many domains. Yet, research examining the effects of perceptions of bias is sparse, possibly due to some prior researchers conflating bias with untrustworthiness. We sought to demonstrate that perceptions of bias and untrustworthiness are separable and have independent effects. The current work examines these differences in the persuasion domain, but this distinction has implications for other domains as well. Two experiments clarify the conceptual distinction between bias (skewed perception) and untrustworthiness (dishonesty) and three studies demonstrate that source bias can have a negative effect on persuasion and source credibility beyond any parallel effects of untrustworthiness, lack of expertise, and dislikability. The current work suggests that bias is an independent, but understudied source characteristic.