Reja admitted earlier this afternoon that he was unsure whether or not to quit his current job in Croatia.
"I have now made my decision," he told Croatian media this evening. "I'm going to Lazio.
"It was not an easy decision and after thinking long and hard about this, I chose to return home. I leave a piece of my heart at Hajduk Split, but I wanted to come back to Italy.
"I've given my word to Lazio President Claudio Lotito."