The 22-year-old grew up in Germany but supported Everton thanks to his father, who will be at White Hart Lane on Sunday.
Holtby admits that it will be emotional but insists that Spurs need to win to continue their path to Champions League qualification.
"It will be third in the Premier League against sixth, and it will be emotional for me to face Everton," Holtby told The Mirror.
"But I am now playing for Tottenham and I am happy at the Lane. We have to end their dreams [of playing in Europe]. We want Champions League football next year.
"[My dad] will be there. I don't know at which end of the ground. He said he is going to wear his Holtby shirt with an Everton badge on it."
Spurs welcome Everton at 2.05pm tomorrow afternoon.