The effort includes personnel from the FBI and other federal agencies, says Trump at a ceremony at the White House where he signs the order.
He describes the decision as "very important due to the crime that is going on".
Memphis, which is located in the state of Tennessee, has had major problems with crime and not least murder for several years. But in recent months, the crimes have decreased and earlier this week, the city's police released a report showing that the number of reported crimes is at its lowest level in 25 years.
Donald Trump has previously deployed the National Guard in Los Angeles and Washington DC.
