The deal for the forward will be completed on January 1 when the transfer window opens.
The striker has been brought in as cover for Wilfried Bony when the forward goes to the African Cup of Nations to represent the Ivory Coast.
The 23-year-old told the Swansea website on his arrival: “I’m really looking forward to it. I already know quite a bit about Swansea and it was their style of play and the ambience at the club that attracted me. It was an easy decision to make.
“The deal was agreed early so I can spend an extra 10 days in Swansea training with the squad and getting to know my new teammates. That way I hope to be ready to offer my services to the team that much earlier.
“I want to prepare properly for the challenge. It’s going to be a big challenge because I have a lot of respect for fellow strikers Wilfried Bony and Bafetimbi Gomis.
“I have to earn the right and respect from the manager and my teammates on the training ground to play. But I’m highly motivated to score goals and help the team.’’
He has big shoes to fill with Bony scoring eight goals from 19 appearances this season, as he builds on his impressive debut season at the club - where he found the net on 26 occasions in 48 games.
Oliveira has only made the two appearances so far this season, and it is evident he has moved to the Liberty Stadium to get some first team football under his belt.