President Obama signed the repeal in December of 2010, but it went into effect September 20, 2011.
The White House released a statement saying "Gay and lesbian Americans now no longer need to hide who they love in order to serve the country they love."
For nearly 17 years, gay and lesbian soldiers were expected to deny their sexuality or face dismissal as part of the controversial policy.
Its repeal has had "no overall negative impact on military readiness," according to a new study.
A research branch of the Williams Institute at University of California Los Angeles Law School released its findings earlier this month.