The singer quit the network after his cameo as a singing soldier was widely mocked.
But he claims he wasn't bothered by anything viewers had to say.
"I came off Twitter coz I was always intending to come off Twitter," he's now posted on Instagram.
"[It] had nothing to do with what people said about my Game of Thrones cameo.
"Why the hell would I worry what people thought about that. It's clearly awesome. Timing was just a coincidence, but believe what you want."
The singer said earlier this month that he wasn't going to read anything on Twitter anymore, but then he took things a step further.
The star's had an on-off relationship with Twitter for a while.
In 2016, before the release of his album ÷ (Divide), the singer "took a break" from social media for a whole year.
He said he was sick of seeing the world "through a screen" and wanted to "travel the world and see everything [he had] missed".
Not all the reaction to the singer's appearance on Game of Thrones was negative.
Others were just a little bit scathing.
Meanwhile, the singer has revealed he's due to play a character called Brendan in a musical-themed episode of The Simpsons.
He'll be at the centre of a love triangle between Lisa Simpson and Nelson Muntz.
"This year continues to be equally surreal and amazing," Sheeran posted on Instagram.
"Watch out for this one, me and Lisa have a whole thing going on."
It will feature in the show's 29th series, which is broadcast in the US in October.