Police responded to the shooting at the NSA's Fort Meade campus after a black SUV rammed a barrier - reportedly at around 7.15am local time.
Within 90 minutes, the agency said the security threat was over and the situation under control.
Cheryl Phillips, Fort Meade Garrison spokesperson, confirmed one person had been taken to hospital after being injured in the shooting.
However, local media reported that three people were injured and one arrested, but this has not been confirmed.
On Twitter, FBI Baltimore wrote: "The #FBI is aware of the incident at Fort Meade and we are sending personnel to respond at this time."
It later confirmed the incident had been "contained".
An NSA spokesman told ABC: "NSA police and local law enforcement are addressing an incident that took place this morning at one of NSA's secure vehicle entry gates.
"The situation is under control and there is no ongoing security or safety threat."
US President Donald Trump has been briefed on the shooting, the White House confirmed.
"Our thoughts and prayers are with everyone that has been affected," it said in a statement.
An aerial image, seen from a WRC-TV helicopter, shows police and fire response vehicles outside the NSA gates.
Bullet holes can be seen in the SUV's front window and the air bags have been deployed.
A man appears to be handcuffed and surrounded by police.
According to Fox5, the incident happened close to the visitors' gate at around 7.15am local time (12.15pm GMT).
The National Security Agency is an intelligence agency of the US Department of Defense.
The secretive agency uses technology, including monitoring the internet, to track the government's adversaries.
In March 2015, two people tried to drive a SUV through the NSA's gates and were shot at by officers when they refused to stop.
One of the vehicle's occupants was killed.
