Spanish top seed Alcaraz, who beat Denmark's Holger Rune in his quarter-final on Wednesday, admitted "probably it is true" when asked about the issue in his post-match press conference.
"My father is a huge fan of tennis," he said after his impressive 7-6 (3), 6-4, 6-4 victory on Centre Court.
"He doesn't only watch my matches. I think he gets into the club at 11:00am, gets out at 10:00pm, watching matches, watching practice from everyone.
"Being able to watch Djokovic in real life, yeah, probably it is true he's filmed the sessions."
U.S. Open champion Alcaraz, who is through to his first Wimbledon semi-final, remains on track for a potential title showdown with defending champion Djokovic on Sunday.
But he denied any filming would give him a competitive advantage.
"I don't think so," he said. "I mean, I have a lot of videos from Djokovic on every platform. I think it's not an advantage for me."
Alcaraz admitted it had been tough to face his friend and fellow 20-year-old Rune.
"It's not easy to play against someone that I've played so many times," he said. "When we were younger, we grew up together, same age. For me is not really easy to play against."
The world number one said he was looking forward to his last-four clash against Russian third seed Daniil Medvedev.
"He's playing great here on grass," he said. "He has had a great, great year as well... but I am going to enjoy the semi-final.
"I think I'm playing great, a lot of confidence right now. So it's going to be a really good match I think."
