Oleg Sentsov, 43, was freed after spending five years in a Russian prison colony above the Arctic circle on charges of plotting a terrorist act. He was flown from Moscow to Kyiv with 34 other former prisoners Saturday.
Speaking at his first news conference, Senstov said he would work to get other Ukrainians out of prison, as well as Russians who were jailed for opposing their government.
"I'll do my best to attract attention to this issue - our political prisoners and Russians - so that it doesn't go away," he said.
The prisoner trade seen as an important step to improving ties between the two countries, which also are strained by Russia's backing of separatist rebels fighting troops in eastern Ukraine.
Sentsov looked composed on a stage inside a Kyiv community center he fielded questions from journalists. In his answers, he indicated he did not hold all Russians responsible for his experience.
"Apart from our prisoners, there are people in Russia who are fighting for themselves, for a free Russia and for our Ukraine. These are our true brothers," Sentsov said. "They all need our help."
He specifically mentioned a Moscow activist, Konstantin Kotov, who received a four-year prison term for participating in a number of unauthorized protest rallies.
Protest leaders were jailed for weeks and more than a dozen people were charged with rioting.