The 26-year-old right-back had two years left on his existing deal, which he signed after completing a permanent move from Sporting Clube de Portugal in the summer of 2023. That switch followed an initial loan spell from January of that year, with Tottenham paying £40m to make it permanent.
Spurs have not confirmed the exact length of the new terms, though reports indicate the contract runs to June 2031 with an option to extend to 2032. The deal also includes a significant pay rise for the Spaniard, reflecting his standing as one of the squad's key performers.
Porro has made 152 appearances for Tottenham Hotspur since arriving in north London, including 47 across all competitions last season, more than any other player in Roberto De Zerbi's squad.
Tottenham Hotspur's sporting director, Johan Lange, praised the defender's development since his arrival.
"During the past three-and-a-half years, he has made huge progress to become one of the best full-backs in the game, and the fact he is about to play in the World Cup for Spain is testament to that," said Lange.
He added that Porro's mentality made him central to the club's plans going forward.
"His character, work ethic and quality are exactly what we look for when building a squad capable of competing at the highest level, and we are delighted that he has chosen to continue his journey with the club."
Manager De Zerbi, who took charge at Tottenham following his exit from Brighton, echoed those sentiments and pointed to the right-back's attitude on the training ground.
"As well as his technical quality, I also love his mentality. Every day he wants to work, to learn and to improve, and these are the characteristics that help players reach the highest level," said De Zerbi.
He went on to highlight the tactical understanding that has made Porro a regular fixture under three different Tottenham managers.
"He understands football in a very intelligent way, and brings energy, intensity and personality to the team."
The timing of the announcement comes with Porro away on international duty. He is currently with Spain at the 2026 World Cup, where La Roja open their group campaign against Cape Verde in Atlanta on Monday.
Manchester City had been mentioned as a potential suitor for Porro, whose performances since 2023 elevated his profile considerably. Tottenham, though, were never prepared to entertain a sale, and instead moved to reward the player they consider central to their long-term plans at right-back.
For a club that has cycled through options in that position in recent seasons, locking down a player of Porro's consistency removes one significant variable from the squad-building puzzle. It also sends a message to the rest of the dressing room about how Tottenham intend to treat players who deliver.
With De Zerbi now settled into the role and a new contract in place for one of his most reliable performers, Tottenham's focus turns to how they build around their right-back for the season ahead. Porro, for his part, has a World Cup to focus on first, and a new deal to enjoy once he returns.