The This Morning host announced the news during an emotional appearance on Friday's show, telling his co-presenter Holly Willoughby that he had "been coming to terms with the fact that I am gay".
Following an outpouring of support, Schofield, who has been married to wife Steph for more than 20 years, sent a message of thanks to fans.
Writing on his Instagram Story, he said: "You will never know how important your support has been today, I've read as much as I can.
"Please please, no matter your age or your thoughts, TALK to someone, don't let your head beat you and hopefully you'll find out that your friends & family have a remarkable ability to surprise you with their love and understanding."
He added the hashtag #bekind.
Earlier in the day he told viewers wrestling with the decision had "caused many heartbreaking conversations at home".
"You never know what's going on in someone's seemingly perfect life, what issues they are struggling with, or the state of their wellbeing - and so you won't know what has been consuming me for the last few years," he wrote.
"With the strength and support of my wife and my daughters, I have been coming to terms with the fact that I am gay.
"This is something that has caused many heart-breaking conversations at home. I have been married to Steph for nearly 27 years, and we have two beautiful grown-up daughters, Molly and Ruby. My family have held me so close: they have tried to cheer me up, to smother me with kindness and love, despite their own confusion, Yet still I can't sleep and there have been some very dark moments."
The 57-year-old's statement added: "Steph has been incredible - I love her so very much. She is the kindest soul I have ever met. My girls have been astonishing in their love, hugs and encouraging words of comfort.
Phillip Schofield talks to his ITV This Morning co-presenter Holly Willoughby about his decision to come out as gay
"Both mine and Steph's entire families have stunned me with their love, instant acceptance and support. Of course they are worried about Steph, but I know they will scoop us both up. My friends are the best, especially Holly, who has been so kind and wise - and who has hugged me as I sobbed on her shoulder. At ITV, I couldn't hope to work with more wonderful, supportive teams."
Following his annoucement, Mr Schofield's This Morning co-host Holly Willoughby posted a picture of the two of them on her Instagram with a caption saying she had "never been more proud of my friend than I am today."
Appearing together on the show, which on Friday morning is normally hosted by Eamonn Holmes and Ruth Langsford, Ms Willoughby told Schofield that she could "feel the relief" from her co-presenter.
"It's funny because everyone I have spoken to, you, have all been so supportive, so loving and caring," Mr Schofield said.
"My entire family, to a person, have grabbed us and said 'It's OK, we love you, we are proud of you,' and every person I tell, it gets a little lighter and a little lighter.
"But at the same time I've made this decision, which is essential for me and for my head, which is the reason why I've done this, I'm very aware that Steph and the girls are at home watching this.
"They have been supporting this as, we got to this moment."
Ms Willoughby commented that Mr Schofield had been very open and honest with his wife, Steph.
“I’ve never had any secrets, we’ve never had any secrets,” he replied.
Asked by Ms Willoughby how Steph was coping, Mr Schofield said: “Yeah, it’s tough, but this is not something that’s happened quickly, I’ve had to deal with this in my head for quite some time.
“We’ve been honest and open. .. Steph… I can’t write in any statement what I feel about that woman. She’s amazing, she’s incredible. There is no one in my life who would have supported me the way… as a wife, as the way she’s supported me. She’s astonishing, literally astonishing.”
Mr Schofield said that his hand had not been forced to share the news, saying: “No. This is my decision. This is my decision. This is absolutely my decision. It was something I knew that I had to do.
"And I don’t know what the world will be like no, I don’t know how this will be taken or what people will think. But what I would say is, ‘Yes I am very, very conscious of the hurt' and so my overriding emotion for my family is obviously going to be guilt because I do feel guilty that this can’t be anything other than a painful process."
The duo were then joined by Mr Holmes and Ms Langsford.
After a round of hugs, Mr Holmes said: "Nobody should be embarrassed about their sexuality and it's fantastic you have spoken out and there will be so many people who have been strengthened by what you've said."
He added that he and wife Ruth would be "the first to stand by you".
LGBT equality charity Stonewall congratulated Schofield on his "hugely personal" decision.
"Incredibly brave and moving announcement from Phillip Schofield this morning," the charity wrote.
"It takes a lot of courage and is always a hugely personal decision to be open about who you are. Congrats Phillip."
Comedian Matt Lucas commented on Twitter about the news that presenter Phillip Schofield has come out as gay.
He said on Twitter: "I'm not surprised about Philip Schofield. Growing up I remember him presenting with Gordon the Gopher from inside that closet!
"Joking aside, that cannot have been an easy statement to make. People come out at different stages in their lives. Good luck Philip."
Actor and comedian David Walliams said on Twitter: "I am sending all my love to Phillip Schofield today. I have always held him in the highest regard, and now have nothing but respect and admiration for him.
"Let's hope we are moving towards a world where no-one has to come out anymore, they can just be who they are and celebrate that."
Schofield said one of the reasons he took the decision was due to the number of "brave" people he has interviewed on the This Morning.
One of those was Towie star Charlie King who came out on the programme in 2014.
"Phillip was so supportive of me that day, I remember being quite doubtful of wanting to do it," King told ITV News.
"I just remember Phillip being so warm and encouraging and embraced me in a way that kind of gave me that reassurance that it's going to be alright.
"He gave me this hug, that I will never forget, and it was that 'yes, I am going to do this, this is right for me'."