The 21-year-old is the only openly gay top-flight male footballer in the world.
In his video, he said: "There's something personal that I need to share with everyone. I am a footballer and I am gay."
His open letter stated: "It's been a journey to get to this point in my life, but I couldn't be happier with my decision to come out. I have been fighting my sexuality for six years now and I'm glad I can put that to rest.
"Growing up, I always felt the need to hide myself because I was ashamed. Ashamed I would never be able to do what I loved and be gay. Hiding who I truly am, to pursue a dream I always wished for as a kid, to play football and be treated equally never felt like a reality."
The conversation around the lack of openly gay male elite footballers has been growing in recent times, and Cavallo is hopeful that his statement will help others to find the courage to follow suit.
"I want to help change this," he said. "I want to show that everyone is welcome in the game of football and deserves the right to be their authentic self.
"It is astonishing to know that there are currently no gay professional footballers who are out and actively playing, not only in Australia, but around the world. Hopefully this will change in the near future."