The champion showed his full array of punches, but was not able to deliver a knockout blow against the battle-hardened 37-year-old.
However, Eubank Jr’s superiority was reflected on the scorecards, with victory secured by 118-110, 118-110 and 120-108 as he inflicted just the sixth defeat of Abraham’s career.
The win means the Brit will take his place in the first World Boxing Super Series beginning this autumn.
Eubank Jr will first take on Turkey’s Avni Yildirim and faces the prospect of a £38million fight against WBA champion George Groves in the final in May 2018.
His win over Abraham, who has previously held who has held middleweight and super-middleweight title, came in convincing fashion as he won the unanimous backing of the judges.
After the fight, Eubank set his sights on Groves’ WBA belt. He said: “They’re all hard, he’s the most durable opponent I’ve faced.
“I hit him with every punch in the book. The statement was made.
“I’m happy with the performance. I got to show my skills, I got to go the 12 rounds and get the experience in.
“I’m going into the tournament to take this man’s belt [Groves].”