Wrampling made his Super Rugby Pacific debut for the Chiefs earlier this season against the Drua. The St Paul's Collegiate graduate has worn New Zealand's black for the NZ Schools and NZ Under-20 sides.
The younger brother of Chiefs back Gideon Wrampling, Malachi, said he is looking forward to joining the Blues.
"The Blues play a physical brand of rugby and I'm looking to learning from the experienced players in the squad and continuing to grow my game."
Slater, 26, already has 68 caps with the Chiefs since his Super Rugby debut in 2019.
A Taranaki veteran from New Plymouth Boys' High School, he played for NZ Under-20 in 2019.
"The Blues have built something special in recent years and I'm excited to contribute to that. It's a fresh start, and I'm keen to get stuck in."
Blues general manager of Rugby Murray Williams said Wrampling was the ideal player for the side and had only scratched the surface of his potential.
"He's the kind of player you want in your environment, hungry to learn, fearless on the field, and built for the modern game.
"Brad is a hardened Super Rugby player who brings an edge to our front row along with great leadership qualities. He's a tough, smart and a great set piece technician."
The Crusaders have extended loose forward Xavier Saifoloi's contract until the end of the 2027 campaign.
Saifoloi, 22, made his Crusaders debut against the Force earlier this year, having made his first-class debut for Waikato in 2023.
"I'm here to be a Crusader. I'm here to learn and grow, as a player and as a person.
"The main driver for me to stay around is how much people care for each other here.
"David Havili mentioned in our pre-season that we needed everyone all in, and that showed and helped our success on and off the field."