We address how to conceptualize and measure intentional self-regulation (ISR) among adolescents from four cultures by assessing whether ISR (conceptualized by the SOC model of Selection, Optimization, and Compensation) is represented by three factors (as with adult samples) or as one “adolescence-specific” factor. A total of 4,057 14- and 18-year-old youth in Canada, Germany, Iceland, and the US participated. Confirmatory factor analyses did not confirm a tripartite model of SOC in any sample, whereas a single (nine-item) composite fit in all samples. A partial weak factorial invariance model showed a roughly equivalent meaning of the nine-item composite among German, Icelandic, and US youth. We discuss the need for further examination of the relative importance of items among Canadian youth, and possible problems using reverse-coded items with adolescents. The similarities that were observed across age and cultural groups suggest that a single factor structure of SOC, as measured by nine items, may be robust for youth in Western cultural settings and that SOC processes are not fully developed until adulthood.