The Deadpool actor posted an emotional message on social media to mark the end of May, which is also Mental Health Awareness Month.
He said his anxiety causes him to 'overschedule, overthink, overwork, over-worry and over-everything', but hope that by speaking out he could help others realise that they are not on their own.
Reynolds, 44, wrote: "May is almost over. It's also Mental Health Awareness month. Which brings me to this.
"One of the reasons I'm posting this so late is I overschedule myself and important things slip. And one of the reasons I overschedule myself is my lifelong pal, anxiety.
"I know I'm not alone and more importantly, to all those like me who overschedule, overthink, overwork, over-worry and over-everything, please know you're not alone.
"We don't talk enough about mental health and don't do enough to destigmatize talking about it. But, as with this post, better late than never, I hope..."
The star has previously spoken about his anxiety, saying back in 2018 that it is something he has always suffered from, and that it is 'not fun'.
Speaking to the New York Times, Reynolds said: "I have anxiety. I've always had anxiety.
"Both in the lighthearted 'I'm anxious about this' kind of thing, and I've been to the depths of the darker end of the spectrum, which is not fun."
He added that he is able to overcome anxiety by focusing on his character. "When the curtain opens, I turn on this knucklehead," he says, "and he kind of takes over and goes away again once I walk off set."
Reynolds also told the outlet that he learned to be a 'skin-covered micro manager' at a young age due to his volatile father, a retired police officer-turned-wholesaler.
To try and ensure that arguments did not break out, he often found himself doing whatever he could to reduce the likelihood of conflict.
Reynolds said: "When you stress out kids, there's a weird paradox that happens because they're suddenly taking on things that aren't theirs to take on."
He continued to say that he tried to combat his anxiety during his 20s with partying, explaining: "I was partying and just trying to make myself vanish in some way."
However, Reynolds added that he eventually calmed down after a number of friends died of overdoses.
Find out more about anxiety and ways to help manage it on the Mind website.