Research has shown that various individual factors play an important role in the underachievement of gifted students. Most often discussed as predictors of underachievement are motivation, learning behavior, and emotions. To examine which specific constructs from these fields simultaneously predict underachievement among gifted fourth graders, logistic regression was performed on data from eighty-five highly intelligent students out of thirty-four classrooms. Students reported on their self-efficacy, learning goal orientation, use of text-reduction strategies, anxiety, boredom, anger, and enjoyment. Emerging predictors of underachievement were self-efficacy, use of text-reduction strategies, and anxiety. As these constructs are all connected to self-regulated learning in different ways, an intervention was implemented which successfully encourages self-regulated learning among students of differing cognitive abilities. Assessing the intervention's effectiveness for different ability levels was important as the intervention was not a pull-out program, but was integrated into regular classroom instruction in which all students in these classes participated. Results from multilevel longitudinal models showed positive intervention effects for learning behavior among gifted underachievers, but no intervention effects on self-efficacy and anxiety could be detected.