The package is in the region of £34.2m (€40m) with add-ons. A 15 per cent sell-on clause is included.
Atletico have been long-term admirers of the Argentina international, and there was an expectation that Spurs would allow captain Romero to depart this summer if the right offer arrived.
- Transfer Centre LIVE! | Tottenham news & transfers⚪
- Got Sky? Watch Premier League games LIVE on your phone📱
- Not got Sky? Latest Sky Sports deals or stream PL games with no contract📺
The central defender was always believed to have preferred a move to Atletico, with Inter Milan and Spurs' north London rivals Arsenal among the other clubs to have been interested.
Romero's Spurs deal us due to run until the summer of 2029.
The 28-year-old was sent off twice last season during Spurs' Premier League relegation battle. He then missed the end of the campaign due to a knee injury.
Romero received criticism from supporters when he appeared to be set to watch his boyhood club Belgrano play River Plate in the Argentina Primera Division Apertura final instead of being at Tottenham's crucial last game against Everton. Romero did, though, attend the final game of the season, in which Spurs secured Premier League survival.
He has made 124 appearances for the club over five seasons, scoring 12 goals and being shown four red cards in the Premier League.
O'Hara: Time for Romero to move on
Speaking on Sky Sports' Tottenham summer special podcast, which will be available to listen to from midday on Thursday, ex-Spurs midfielder Jamie O'Hara said of Romero:
"He's a bit of a liability. When he plays, he costs us games, points and red cards.
"I just think his attitude towards the board and the way he was, I just think it's, 'All right, thank you, and we're going to move on'.
"We've finished 17th the last two seasons, and he's been involved. He was captain last season, and the way he acted at the end of the season, when he got injured and we all saw him crying, that wasn't for Tottenham; it was more for Argentina and his World Cup.
"And then he goes to Argentina on the last day of the season, and everyone's like, 'Where's Romero?' So that situation for me needs to be put to bed. I don't think we need any of that bad publicity around us.
"Get as much as we can for him; let him move on. We've got back up now with Van Hecke and Senesi, so thank you, see you later."
Spurs are set to make a loss on Romero, who joined from Atalanta for around £42m in the summer of 2021.
O'Hara said of Atletico's £34.2m deal for Romero: "The problem is there's a premium for English clubs, who will pay over the odds for people with European clubs inflating the fee.
"The problem is if you're going to go and sell him to Atletico Madrid, they haven't got the money.
"If we were selling him to Man United, we could probably get £60m-70 m for him. But the problem is if you sell a player to Europe, they just don't have the money that the Premier League clubs have, so you have to accept that it's going to be a lesser fee than what maybe you think you can get for him.
"He wants to go to Atletico Madrid. He just feels like an Atletico Madrid player. I just feel like you've just got to take that one on the chin and move on from it."
