Since Arians's arrival at the club he has transformed the Cardinals into a strong outfit in the NFC West, guiding them to back-to-back 10-win seasons for first time since the 1970s.
Keim, meanwhile, has helped to forge a solid roster since he was promoted to the GM position in 2013.
"Two years ago we hired Steve and Bruce a few days apart and believed we had something really special," president Michael Bidwill said in a statement. "Every day since then they have done nothing but validate that belief.
"The team's performance over the last two seasons certainly reflects how talented they are in their respective roles and it was important that we reward them for their accomplishments.
"I speak not only for myself but for all Cardinals fans when I say how thrilled we all are that Steve and Bruce are now under contract through 2018."
The Cardinals reached the playoffs for the first time since 2009 last season before they were defeated in the wildcard round by the Carolina Panthers.