Gemini 6A was launched on December 15, after a three-day-long delay due to a malfunction and engine shutdown immediately after ignition. It entered into an 87-by-140-nautical-mile (161 by 259 km) orbit, and was briefly visible from Gemini 7 just after launch. Borman and Lovell were also able to see the contrail from the launch.
The plan called for the rendezvous to take place on the fourth orbit of Gemini 6A. Their first burn came 94 minutes after launch when they increased their velocity by 16.5 ft/s (5.0 m/s). Due to their lower orbit they were gaining on Gemini 7 and were 634 nautical miles (1,174 km) behind. The next burn was at 2 hours and 18 minutes when Gemini 6A made a phase adjustment to put them on the same orbital inclination as Gemini 7. They now only trailed by 261 nautical miles (483 km).
The radar on Gemini 6A first made contact with Gemini 7 at 3 hours and 15 minutes when they were 234 nautical miles (433 km) away. A third burn put them into a 146-by-148-nautical-mile (270 by 274 km) orbit. As they slowly gained, Walter Schirra put Gemini 6A's computer in charge of the rendezvous, and at five hours and four minutes, he saw a bright object that he at first thought was the star Sirius, but was in fact Gemini 7.
After several more burns the two spacecraft were only 130 feet (40 m) apart. The burns had only used 110 pounds (50 kg) of fuel on Gemini 6A, leaving plenty of fuel. During the next 270 minutes the crews moved as close as 1 foot (30 cm), talking over the radio. At one stage the spacecraft were station-keeping so well that neither crew had to make any burns for 20 minutes.
As the sleep periods approached, Gemini 6A made a separation burn and slowly drifted out to 16 kilometers, to prevent an accidental collision in the night. Gemini 6A reentered the next day, landing within 9.7 nautical miles (18.0 km) of the planned site, the first truly accurate atmospheric reentry.