Launch from Cape Canaveral; landing 1200 km southwest of the Bermuda Islands in the Atlantic Ocean.

After separating from the spent rocket stage, they turned the spacecraft around and tried to perform a rendezvous maneuver with the rocket stage. They spent fifteen minutes formation flying with the stage (closest approach about 6m), but the rocket stage vented its own fuel and that maneuver was stopped.

More successful was another rendezvous maneuver with the later launched spacecraft Gemini 6A. For 270 minutes the crews moved as close as 30 centimeters, talking over the radio. Several stationkeeping maneuvers (cicling each other, approaching, backing off) were performed. It was a really milestone of human spaceflight.

For the first time the astronauts slept and worked together. Their sleep periods were scheduled at the same time unlike previous missions and they were able to get some sleep. 20 experiments were planned, only two of them had been cancelled, but it were only four new experiments. One of the new biological experiments was "Bioassays of Body Fluids." Its purpose was to study the effect of space flight on body fluid chemistries. Other medical experiments were for example calcium balance study and inflight sleep analysis.

Both astronauts set a new flight duration record by that time. The last three days in space the mission began to drag. While in drifting flight, both astronauts red some of their books (authors: Mark Twain and Walter D. Edmonds).

There were a few problems during the flight. There were again problems with the fuel cells und several thrusters worked poorly. A just-used urine collection bag split open early in the mission. The crew never managed to collect all the floating globules, but Lovell later described this flight as '...two weeks in the Men's Room' - not very comfortable.

The reentry was performed without any problems only 12 km of the targeted landing point. The crew was brought to the USS Wasp.