With globalization, digitalization, and the spread of information and communication technologies, rules regulating work have been softened or completely abolished. As a consequence, employees face additional cognitive demands to plan, structure, and coordinate their work. In order to capture these demands of contemporary work, we constructed and initially validated the Cognitive Demands of Flexible Work (CODE) scale. The scale comprises four subscales (i.e., structuring of work tasks, planning of working times, planning of working places, and coordinating with others). We validated the scale in three independent studies (overall N = 1129) in German and English. Confirmatory Factor Analyses supported the four-factor structure as well as the scalar invariance of the different language versions. Moreover, the subscales showed convergent validity with related constructs such as requirements for problem solving or autonomy. Criterion validity for emotional exhaustion, engagement, and positive work rumination, negative work rumination, and problem-solving pondering suggests that cognitive demands of flexible work can be construed as challenge stressors. However, relationships with emotional exhaustion were only significant for one of the four subscales. Overall, the CODE scale was shown to be a reliable and valid instrument to measure cognitive demands of flexible work.