Samardzija's deal is for $2.64 million, with another $125,000 in incentives. Russell's totals will be $1.075 million, according to a major league source.
"[Cubs president] Theo [Epstein] has never been to arbitration, I've never been," Cubs general manager Jed Hoyer said. "We'll go if we have to go, but if you can work out deals with agents, it's a far better way to go."
In his first year as a starter, Samardzija, who will turn 28 on Wednesday, went 9-13 with a 3.81 ERA in 28 starts. He had 180 strikeouts in 174 2/3 innings.
"Arbitration is definitely something you want to avoid just out of the sheer fact that you want to think you have a good relationship with the staff and front office," Samardzija said. "You want to be here, you want to get the deal done with the least stress as possible and we did that."
The 27-year-old Russell, the Cubs' primary left-handed reliever, appeared in a career-high 77 games last season, posting a 3.25 ERA with 13 holds and a 1.30 WHIP.
"I've heard the process of going to hearings is a pain in the butt, so I wasn't really looking forward to it," Russell said. "I'm happy we got the deal done and no hurt feelings."
With Samardzija and Russell signed, the Cubs, who signed pitcher Matt Garza to a one-year, $10.25 million contract on Thursday, have no more arbitration-eligible players.