The 350-game Blue and Crow details the incident in his new autobiography, The Boy from Boomerang Crescent.
In his book, Betts disclosed the racism he had encountered during his career, with this incident taking place during the week of Sir Doug Nicholls round six years ago.
"In big black Texta right above my head some racist had written the words ‘A** F****T'.
"I sat there speechless for a moment after I'd opened it. Then I was like, ‘Yep — again. Here it is again.'"
The three-time All-Australian was set to talk to the press after training that morning, but immediately called for a meeting with club bosses.
However he revealed he was told to keep quiet on the matter.
"I didn't feel like I could mention the letter without at least telling the club what I wanted to do. When we walked into the meeting with the club, straight away I was looking at all-white faces," Betts said.
"I knew that they would not fully understand what I was about to show them — how stuff like this cuts me to the core, and in particular the effect the word ‘a**' can have.
"I said to the club, ‘listen, I really want to take this piece of paper into this press conference and when the journos ask me why the AFL has the Indigenous Round, I want to say ‘this is why.'"
The Indigenous icon said he wanted to take the letter into the press conference, and perhaps even walk out after showing the media.
Betts continues to say that today he would do it without telling the club first.
"Then the club representatives spoke and Anna (his wife) and I listened … these days, I would do it without even telling them, because essentially they talked us into not saying anything," he wrote.
"Upon reflection, they were trying to minimise any type of media circus before my game, but maybe this was more important than the game itself?"
This comes during a week with renewed focus on the club's infamous 2018 pre-season camp, which Betts' details further in his book.
Further revelations have come, with The Age reporting that several former Crows players are looking to pursue a class action against AFL and the club.
Adelaide lawyer Greg Griffin has been in contact with said players.
"The recent days have not diminished interest from a range of players," Griffin told The Age.
"I've spoken to a number of players over the past 24 hours. I think the release of Eddie's book has intensified the feelings that players who attended the camp had."
Crows skipper Rory Sloane recently spoke with radio station 5AA on the camp, where he shared he was in the same group as Betts but his experience differed.
Sloane, who wasn't captain at the time, said he didn't hear Betts' personal details being shared.
"I was in that group. There was so much going on over the course of that. There was about 10 or 12 of us. There's so much going on during that time that I suppose I didn't pick up on it until Eddie mentioned it to us after. It is sad to think that that's what they used it for and it's not OK," he said.
"It was a really hard thing to manage because some guys found the camp boring. Some guys had a really horrible experience on the camp. Some guys enjoyed their experience on the camp."
The two-time best and fairest winner stood by his comments post camp, that he had 'come back a better husband, father and son'.