This dissertation addresses the persistent "strategy-execution gap," where approximately 60% to 90% of strategic initiatives fail due to a reliance on "rational actor" assumptions that ignore the psychological realities of human behavior. Adopting a two-essay, mixed-methods approach, the research shifts the execution paradigm from structural compliance to the design of "behavioral choice architectures". The first essay utilizes a qualitative multiple-case study of six organizations in the U.S. and Saudi Arabia to deconstruct organizational resistance. It introduces the Influence vs. Resistance Framework, identifying the "Subversive" archetype—high-influence actors who feign agreement while passively stalling implementation—as the most lethal and frequently misdiagnosed threat to execution. Findings suggest that resistance is often rooted in loss aversion, the endowment effect, and status quo bias. The second essay introduces the Behavioral Economics in Execution (BEX) framework, a five-step prescriptive model. Using a policy-capturing experimental design with 33 senior executives (N=1,056 decisions), the study empirically validates five behavioral interventions: piloting with champions, loss-framed score-boarding, public commitments, rigid review cadences, and milestone celebrations. Results provide robust support for the framework revealing that loss-framed KPIs exert the strongest influence on perceived success. The dissertation culminates in an integrated "Behavioral Operating System," providing a scientifically validated "Behavioral Playbook" for leaders to neutralize resistance and transform strategic intent into operational reality.