Max Verstappen traded positions with Charles Leclerc in the day's concluding running at the Sochi Autodrome.
After Leclerc set the pace in the opening running for this weekend's Russian Grand Prix, Verstappen moved to the top of the time charts.
The Red Bull driver finished 0.335 seconds clear of Leclerc, with Valtteri Bottas third.
Lewis Hamilton, who is bidding for his first win since the summer break, was fourth, eight tenths down on Verstappen.
Hamilton's Mercedes team are so often the dominant force in Russia, having won all of the five races staged here.
But Hamilton, 65 points ahead of Bottas in his quest for a sixth world title, looks to have his work cut out to seal a return to the winners' circle after finishing behind both a Red Bull, a Ferrari and his team-mate, too.
Ferrari arrived here as the team to beat, with Leclerc winning successive races in Belgium and Italy before Sebastian Vettel ended his 13-month losing streak in Singapore last weekend.
And with Verstappen to serve a five-place grid penalty following changes to his engine, Ferrari, and Leclerc in particular, looked well-placed to win for a fourth time in as many races.
Vettel, who made a slight mistake on his speedy run, was fifth in the second session, 1.039 sec off the pace.
Despite Verstappen's encouraging form, there was trouble for Alex Albon in the sister Red Bull.
The London-born Thai watched much of the session from the garage as his mechanics worked on damage to the floor of his car before he set a time only good enough for 10th.
Albon also had a near-miss with Hamilton when the championship leader nearly ran into him at the third turn.
British teenager Lando Norris finished 11th, four tenths and six places clear of McLaren team-mate Carlos Sainz.
George Russell was 19th, a full second faster than Robert Kubica in the other Williams.