Hamilton will miss the first four games of the 2014 season and will be eligible to return after the team's Week 4 contest against New Orleans.
The South Carolina product appeared in three games last season as a rookie and recorded a pair of tackles. He has missed two preseason games this month because of a concussion and hamstring injury.
It's the second suspension for a Cowboys defensive back this season. Orlando Scandrick was also hit with a four-game penalty for violating the league's policy on PED use.