In the present research, I develop and validate the Dark Political Skill Scale. Intended to supplement the existing Political Skill Inventory (PSI; Ferris et al., 2005), the Dark Political Skill Scale captures the more covert and deceptive side of political effectiveness in the workplace. Across three studies, I collected data from independent samples of full-time employees (N = 430, N = 157, and N = 142), representing a variety of occupational backgrounds. The 10-item uni-dimensional Dark Political Skill Scale demonstrated consistent evidence of convergent validity. As expected, it was positively related to (though not redundant with) an array of social competencies (political skill, social skill, self-monitoring, and perceived ability to deceive) and political will. I also found evidence of criterion-related validity as the Dark Political Skill Scale was associated with behavioural outcomes, including greater engagement in counterproductive work behaviour and workplace impression management. Dark political skill also acted as an influential moderator in predicting impression management. Importantly, in comparison to the PSI, the Dark Political Skill Scale demonstrated differential relationships with the variables in the present research. Of note, the personality profiles of employees scoring high on dark political skill showed a different pattern of results than the PSI, such that the former were lower in Honesty-Humility, Emotionality, and Agreeableness. Finally, self- and peer-reports indicated low to moderate convergence for the Dark Political Skill Scale, which was interpreted to be suggestive of the deceptive nature of dark political skill. Taken together, the Dark Political Skill Scale offers a novel theoretical and methodological contribution to the organizational politics literature. Supplementing the PSI, this new scale provides the opportunity for a more comprehensive assessment of workplace political effectiveness, and a greater understanding of the competencies required for successful engagement in a full range of political behaviours.