Haslem grew up in Miami’s Little Haiti neighborhood, playing pickup games on cracked courts before earning a scholarship at the University of Florida, where he led the Gators to a national title in 2006. Going undrafted, he signed a modest contract with the Heat, immediately embracing the team’s rebuilding phase under Pat Riley and the nascent "Heat culture" of accountability and toughness.

His first two seasons were marked by bruising defense, rebounding, and a willingness to do the unglamorous work. While his minutes were limited, his presence in the locker room resonated with veteran players, laying the groundwork for the culture that would later support the "Big Three" era.