Voice behavior–the upward communication of challenging, but constructive ideas, suggestions, and concerns–is critical to organizational innovation, safety, and performance. However, supervisors not always welcome or endorse such input provided by subordinates. Organizational newcomers, although ideally positioned to introduce fresh perspectives into organizations, may face particularly great difficulties in getting supervisors to endorse their ideas. In difference to prior research, we rely on sensemaking theory to develop a cognitive account of managerial reactions to newcomer voice behavior. To operationalize our framework, we draw from research on organizational socialization and argue that voice endorsement critically depends on the degree to which newcomers act based on an understanding of the organization’s history, language, and people. We test our model using data from 107 matched pairs of supervisors and newcomers, distinguishing between promotive (idea-oriented) and prohibitive (problem-focused) newcomer voice behavior. As our findings suggest, supervisors are receptive towards newcomer promotive voice, but tend to reject problem-focused input if it comes from ill-socialized newcomers, which, although rather unsurprising from a sensemaking perspective, still deprives organizations of vital input and challenges organizational reliability. We discuss implications for theory and practice.