The youngster has already undergone a medical with the Catalan giants and will now put pen to paper on his contract, per Diario Sport.
Onstein will then join up with Julian Belletti’s Barcelona Atletic side and will hope he can make an impact with the reserve team.
Jong Genk’s technical coordinator Stijn Haeldermans has hailed the youngster’s qualities.
“Juwensley stands out as a central defender for his speed and physical presence, combined with technical experience and good ball control,” he said.
“He is not afraid to penetrate and play with space from the back. In short, he is a modern central defender who fits perfectly with Genk’s footballing vision.”