Kris shared a number of Instagram pictures of herself and the fashion icon over the weekend and the "#secretproject" hashtag made more than a few appearances, reported Digital Spy.
Kris, 60, first uploaded a captionless photo of Lagerfeld setting up for a shoot.
"Just your average Friday night in Paris no big deal... @karllagerfeld #secretproject @kendalljenner," she wrote.
Kendall is currently in Paris for Paris Fashion Week, where she's been modelling for Balmain, Elie Saab and Dior.