Spurs are widely reported to have agreed a deal to sign the 22-year-old for a fee in excess of £4 million ahead of the summer transfer window.
And while Wimmer insists the deal is not yet complete, he has confirmed there have been negotiations over a transfer.
"I do not understand why my phone is suddenly overflowing," Wimmer told Express. "There were negotiations with Tottenham Hotspur, but nothing is fixed yet."
Wimmer, a centre-back, has made 25 Bundesliga appearances this season for Koln, who sit 11th in the Bundesliga.
The defender was back in the starting line-up for the 1-1 draw with Werder Bremen on Saturday having missed the goalless draw with Borussia Dortmund after being sent off in a victory over Eintracht Frankfurt.