Frank said last week that Romero was a player who commands “big respect” from his team-mates and “sets the standards” on and off the pitch.
“What I like about him and why I have chosen him as captain is his leadership qualities,” said the Spurs boss.
“The staff have said to me they’ve never seen him train that well. He’s in a very good place. I see a player that will want to lead the team and push the team.”
The former Belgrano defender, who had two years left on his previous deal, follows right-back Djed Spence in signing a new long-term contract.
Spence, 25, arrived from Middlesbrough in 2022 but endured a difficult start to his Spurs career and had loan spells at Rennes, Leeds and Genoa.
Last season he emerged as an important player for former boss Ange Postecoglou and has made 42 appearances, scoring twice.
Spence’s existing deal had been set to expire in 2028.
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