The two clubs have agreed an undisclosed fee for the 28-year-old, who is expected in Germany for medical tests on Monday.
Should he pass, he will put pen to paper on a four-year contract with the Foals.
"We are getting another versatile and technically strong player for our attack," Gladbach's director of sport Max Eberl said.
"This transfer was not easy to complete which makes us all the more delighted that it has now come off."
Raffael is no stranger to the Bundesliga having played for Hertha Berlin between 2008 and 2012. He also spent the second half of the 2012-13 season on loan with Gladbach's local rivals Schalke, scoring two goals in 16 appearances.
He was also part of the Kiev side which knocked Gladbach out of the Champions League at the play-off stage last August.