The Holland defender is set to join on-loan to the end of this season from AS Monaco.
Dutch sources say Wagner has been key in convincing Kongolo about the move, spending several hours on the phone with the defender last week.
Kongolo has found first team action difficult to come by at ASM and Wagner has assured him he will be granted every chance of establishing himself in the Terriers' defence.
Wagner sees Kongolo as a left-back and is ready to throw him in at the deep end as soon as the deal is rubberstamped.
ASM still regard the Dutchman highly and refused to consider including a buy option in the loan arrangement.