Joe Mendez approached the 18-year-old model and reality star as she made her way through the airport in Miami, surrounded by paparazzi.
Video shows him going up to Kylie as she got out of her car. He walked close to her as she made her way to the check-in desk.
Mendez runs a memorabilia business called Memorabilia For You. He told INSIDE EDITION that he's been collecting autographs since he was 10 and considers it a hobby.
Mendez was arrested in September after he was accused of possession of child pornography.
The 47-year-old Miami detective is also accused of supplying alcohol to minors. There were allegedly pictures of naked underage girls found on his phone.
Mendez has denied all allegations of wrongdoing.