"I'm a little emotionally exhausted because that was super stressful, but it worked", he told a news conference after the rocket lifted off at 2:49 a.m.
Eleven minutes later, the confirmation came from SpaceX mission control: "Dragon separation confirmed".
On March 8, the capsule will undock from the ISS and travel back to Earth.
It's expected to touch down in the Atlantic Ocean, somewhere off the coast of Florida near Cape Canaveral and the Kennedy Space Center. Eastern that day, where SpaceX vessels will recover the spacecraft and return it to Cape Canaveral. The US government is also eager to have the ability to fly to the ISS without buying seats on Russian Soyuz capsules. The Starliner is now due to make its first uncrewed test flight no earlier than April, and its first crewed flight no earlier than August. That mission is now scheduled for launch no earlier than July, with both NASA and SpaceX expecting it will launch before the end of the year.
If the current unpiloted demonstration flight goes well and no major problems develop with other upcoming tests, SpaceX hopes to launch Behnken and Hurley in July for what will be the first piloted US space mission in almost eight years.
The Crew Dragon took off on the six-day journey with the help of a Falcon 9 rocket from NASA's Kennedy Space Center in Florida in the early hours of Saturday morning. NASA selected SpaceX and Boeing to design and build crew-carrying spacecraft to shepherd astronauts to and from the space station - replacements for the Space Shuttle, which NASA retired in 2011.
Russian Federation charges about $80 million per ticket. But the programme has suffered delays as safety requirements are much more stringent for manned flights than for unmanned missions to deploy satellites.
Nasa had announced weather conditions were good head of the launch, with an 80 per cent chance of favourable weather.
"These events remind us. that we can be united by a cause that is not based on fear, threat or common enemy, but rather on a bold endeavor", she said.
Chris Ferguson, commander of the final shuttle flight and now a Boeing executive, will join two other NASA astronauts aboard the Starliner for the company's first piloted launch this fall.
All this particular mission is carrying is a test dummy and 90kg of supplies.
NASA did not want to rely on just one single vehicle, in case of accidents. That flight is now slated for July.
With the successful launch and docking procedure now behind it, only one important test remains for SpaceX's test flight: the return trip.
The missile, named Crew Dragon, is on a test run and will possibly be used to send American astronauts to the International Space Station, perhaps as early as July.