Racial identity invalidation is a social identity threat that occurs when a person’s racial or ethnic group membership is denied by others. While this phenomenon can be experienced by people of all backgrounds, it is particularly prevalent among multiracial people, whose mixed-race identities do not neatly fit the categories typically used to define race. Racial identity invalidation has been associated with several negative effects on mental health, social relations, and physical and emotional well-being; yet, because multiracial issues and experiences often go unnoticed in our largely monoracial society, this form of multiracial microaggression has been overlooked in discussions of diversity, equity, and inclusion. Moreover, little research has explored how identity invalidation plays out specifically in the workplace setting—an important context tied to one’s livelihood—making it unclear what downstream effects invalidation may have on work outcomes such as job satisfaction, engagement, and team cohesion. The present study expands on prior research by exploring how multiracial identity invalidation unfolds in various work contexts, with a focus on how multiracial people respond to instances of invalidation at work and what consequences these events might have for their professional relationships and career advancement. Qualitative data were collected through an online questionnaire and one-on-one, semi-structured interviews with multiracial people of diverse backgrounds and industries. Using a constructivist grounded theory approach, the study aimed to better understand the experiences, responses, outcomes, and contextual factors related to this phenomenon, with the ultimate aim of inductively developing a comprehensive model of multiracial identity invalidation in the workplace. Findings from this study suggest that multiracial people experience similar types of invalidation incidents (e.g., being asked to prove one’s heritage) in the workplace as they do in other arenas of life, yielding similarly negative intrapersonal responses (e.g., hurt, resentment, self-doubt). However, due to the power dynamics at play in most workplaces, their options for how to outwardly respond to these invalidation incidents are often limited, with responses ranging from passive (e.g., laughing it off) to more active approaches (e.g., trying to create a learning opportunity), depending on the perceived risk and likelihood of change. Although repeated invalidation experiences can lead to several negative work outcomes (e.g., strained coworker relationships, disengagement, self-silencing), some of the study participants also made changes for the better, by seeking new work opportunities at organizations that embraced their full and complex identities, aligned with their personal values, and recognized the strengths of having a mixed-race perspective. Finally, this study noted several contextual factors that appeared to influence the process of invalidation, with a particular emphasis on the need for social support systems and inclusive organizational practices. These study findings and the resultant comprehensive model offer practical insights for individuals, teams, and organizations, and suggest avenues for future research into the topic of multiracial identity invalidation in the workplace.