Inter’s sixth win in a row across all competitions, and fourth in succession in Serie A, sends them into the international break in high spirits.
Icardi made an early breakthrough in Ferrara and then slotted a precise finish for a 79th-minute winner after SPAL had briefly drawn level through Alberto Paloschi.
The double from Inter’s prolific Argentinian puts the Nerazzurri at the head of a pack who will be aiming to provide competition for Juventus, the soaraway leaders, and Napoli, who sit second.
Inter took a 14th-minute lead when Icardi headed home, directing the ball down and in off the left arm of defender Johan Djourou, with the bounce deceiving goalkeeper Alfred Gomis.
The visitors should have been almost instantly pegged back, but SPAL’s Mirco Antenucci failed from the penalty spot after Inter defender Miranda fouled fellow Brazilian Felipe. Antenucci’s kick fizzed low and wide of the left post, to his obvious embarrassment.
Gomis then foiled Icardi as Inter, at the other end, pushed for a second goal.
Inter kept probing and Thiago Cionek had to hack away as Icardi again lurked, before SPAL themselves came close to scoring as Samir Handanovic denied Felipe moments before the break.
Andrea Petagna wasted a great chance for SPAL as the midway point approached in the second half, firing over the Inter bar.
Boss Luciano Spalletti had told Inter to treat the fixture like a Champions League game, but they were in trouble in the 72nd minute when Paloschi drew SPAL level, turning in a deflected cross sent over from the left flank.
Icardi came up trumps again though, finding space in the penalty area to meet a clever through-ball from Ivan Perisic and fire home.
Perisic cleverly created space for himself, weaving from his station on the left and into midfield before sliding the ball through a barely perceptible gap for Icardi, who accepted the gift of being left unmarked and curled his shot around Gomis and into the right corner.