At the Athens Olympics in 2004, Hennagan was part of the US team which finished first in the 4×400 meters relay. This result has been in doubt since 2010 after Crystal Cox, who ran for the team in a preliminary round, admitted to using doping. Cox's drug violation puts the entire teams gold medal in jeopardy, however as of 2012 the American team ( apart from Cox ) retain their gold medals.
In 2008, Hennagan had her relay medal from the 4 X 400 metre relay from 2000 Olympics stripped because of teammate Marion Jones admitting to performance enhancing drug use. On July 16, 2010, She and 6 other members of the US Women's Track and Field team won their appeal to the IOC to have their medals reinstated.