Mauro Icardi's penalty proved decisive as Inter Milan defeated Real Betis 1-0 in Lecce to end an impressive pre-season campaign on a high.

In the week he was named in the Argentina squad, Icardi scored the only goal of the game in the first half, converting a spot-kick he had won himself.

New signing Dalbert, brought in for a reported €20 million ($29.8 million) from Nice, made his debut and played for 72 minutes.

Good recent form has seen Inter record friendly wins over the likes of Lyon, Chelsea, Bayern Munich and Villarreal, with Luciano Spalletti's men tasting victory once again to go into next week's home Serie A opener against Fiorentina in good spirits.

Real Betis beat AC Milan in an entertaining friendly on Thursday (AEST), but it could not repeat the trick against the city rival of Vincenzo Montella's men, Sergio Leon missing a good chance in either half.

Quique Setien's men open their LaLiga season with a daunting away match against Barcelona on 21 August (AEST).

Betis should have taken the lead when Leon squandered a great early chance, firing over from an unmarked position 12 yards out after being set up by Antonio Barragan.

Ivan Perisic had an ambitious overhead kick from a tight angle punched away by Betis keeper Antonio Adan at the other end, before Matias Vecino headed just wide from the resulting corner.

Inter moved ahead on the half-hour mark, with some calamitous Betis defending giving them the opportunity.

A weak back-pass from Aissa Mandi allowed Icardi to seize possession and round Adan, who then brought him down for a penalty, despite the former Real Madrid shot stopper's fierce protests.

Icardi then took the spot-kick himself and confidently sent Adan the wrong way with a powerful effort.

After Icardi and Joao Mario came off at half-time, Samir Handanovic made his first save, stretching to hold Juanjo Narvaez's attempt. 

Eder, who replaced Icardi, saw a powerful 30-yard free-kick deflect narrowly wide for Inter.

Leon's poor night for Betis continued as he squandered another great chance, taking a touch and firing over after an excellent throughball from Joaquin.

Another Narvaez effort narrowly missed the target as Spalletti's side held on for victory and a clean sheet.