Under the new policies, any officer who is given a religious exemption will be allowed to keep a beard up to a half-inch in length and wear a blue turban with a Police Department hat shield on it.
Both the Muslim Officers Society and the Sikh Officers Association pushed for the change in policy, according to The New York Times. Together, the groups have more than 1,100 members. O'Neill said Wednesday that there are about 160 Sikh officers on the police force.
The Sikh Officers Association took to Twitter to praise the decision.
On Facebook, the NYPD Muslim Officers Society highlighted Wednesday as a "proud moment" for the Police Department, the city and the country.
"People can elect to serve their communities without having to compromise their faith, or letting go of their dreams (because) it doesn't have place for your faith," the group wrote.
The New York Police Department joins a handful of agencies that allow facial hair and turbans, according to The New York Times, including the U.S. Army and police departments in Washington, D.C. and Riverside, California.