This chapter explores gifted underachievement as a developmental process shaped by changing beliefs, motivation, and environmental fit. The Achievement Orientation Model (AOM) provides the central framework, emphasizing that achievement depends on self-efficacy, goal valuation, and environmental perceptions, with self-regulation translating these beliefs into performance. Misalignment in any domain can lead to disengagement, but underachievement is not fixed and can be reversed through targeted interventions. The chapter situates the AOM alongside related theories and models, including Snyder and Linnenbrink-Garcia’s Pathways to Underachievement and Rimm’s Trifocal Model. Practical strategies are highlighted through the “Three Legs of Talent Development,” which uses advanced content, stimulating instruction, and interest-based authentic learning to foster confidence, engagement, and support so that gifted students can thrive.