Launch from the Baikonur Cosmodrome and landing 540 km northwest of Karaganda (53. latitude grade).

The launch was scrubbed several times due of technical problems and excessive solar flare activity. The cosmonaut was originally intended to stay in orbit for eight days, but the spacecraft ended up in a lower than planned orbit. Combined with increased atmospheric activity due to solar levels, Vostok 5 quickly decayed and temperatures in the service module reached very high levels (up to 30°C) and turned down on the 3rd day to only 10°C. So, the mission had to be shortened.

Mission objectives were officially: further study of the effect of various spaceflight factors in the human organism; extensive medico-biological experiments under conditions of prolonged flight; further elaboration and improvement of spaceship systems, but no results were published. Unlike earlier missions, only a black and white film camera was carried. Photometric measurements of the earth's horizon were made.

It was a rendezvous flight with Vostok 6 (4.5 km distance) at time. There was directly communication between both capsules during the closest approach. Later on, the cosmonaut performed communications experiments with submarines and airplanes.

A problem with the spacecraft's wast collection system (probably a spill) made conditions "unpleasant" in the capsule. Once again, the Vostok service module failed to separate cleanly from the reentry sphere. Wild gyrations ensued until the heat of reentry burned through the non-separating retraining strap. But all in all, it was the longest flight duration of a spacecraft until that time.

Many errors occurred in the entire landing sequences, including actions of the VVS recovery forces. Both spacecraft landed two degrees of latitude north of the aim point. It was calculated that this could have occurred by duplicate landing commands having been sent, but such a failure could not be duplicated in postflight tests of ground equipment.

Valeri Bykovsky was originally intended to stay in orbit for eight days, but the mission details changed many times due to elevated levels of solar flare activity at the time and he was eventually ordered back after five days. This remains the record for solo manned flight in Earth orbit.