On 16 July, Persano took the Italian fleet out of Ancona, bound for Lissa, where they arrived on the 18th.
With them, they brought troop transports carrying 3,000 soldiers; the Italian warships began bombarding the Austrian forts on the island, with the intention of landing the soldiers once the fortresses had been silenced.
In response, the Austrian Navy sent the fleet under Tegetthoff to attack the Italian ships.
Re di Portogallo was at that time in the 3rd Division, along with the ironclads Terribile, Formidabile, and Regina Maria Pia, and the coastal defense ship  Varese.
After spending the 18th unsuccessfully bombarding the Austrian fortresses, the Italians withdrew late in the day, preparing to launch another attack the following morning.
 Persano sent most of his ships to bombard the town of Vis, but he was unable to effect the landing.

The next morning, Persano ordered another attack; four ironclads would force the harbor defenses at Vis while Re di Portogallo and the rest of the fleet would attempt to suppress the outer fortifications.
This second attack also proved to be a failure, but Persano decided to make a third attempt the next day.
Re di Portogallo and the bulk of the fleet would again try to disable the outer forts in preparation for the landing.
Before the Italians could begin the attack, the dispatch boat Esploratore arrived, bringing news of Tegetthoff's approach.
Persano's fleet was in disarray; the three ships of Admiral Giovanni Vacca's 1st Division were three miles to the northeast from Persano's main force, and three other ironclads were further away to the west.
Persano immediately ordered his ships to form up with Vacca's, first in line abreast formation, and then in line ahead formation.
Re di Portogallo initially had trouble getting her engines running, but after repairs were quickly made, she joined the rest of the fleet.
She was one of the last ships in the line.

Shortly before the action began, Persano decided to leave his flagship and transfer to Affondatore, though none of his subordinates on the other ships were aware of the change.
They were thus left to fight as individuals without direction.
More dangerously, by stopping Re d'Italia, he allowed a significant gap to open up between Vacca's three ships and the rest of the fleet.
Tegetthoff took his fleet through the gap between Vacca's and Persano's ships, in an attempt to split the Italian line and initiate a melee.
He failed to ram any Italian vessels on the first pass, so he turned back toward Persano's ships, and took Re d'Italia, San Martino, and Palestro under heavy fire.
The Austrians quickly inflicted serious damage on Re d'Italia and Palestro, eventually sinking both ships.
After Palestro withdrew, the Austrian ironclads turned their attention to the 3rd Division, including Re di Portogallo.

Re di Portogallo initially attacked the unarmored ships Erzherzog Friedrich and Kaiserin Elizabeth before the ship of the line Kaiser rammed Re di Portogallo in an attempt to save them.
Kaiser struck only a glancing blow, however, and inflicted little damage.
Re di Portogallo fired her light guns into the ship in response, starting a fire, and killing or wounding a number of Austrian gunners before Kaiser could break free.
By this time, Re d'Italia had been rammed and sunk, and Palestro had been set on fire, soon to be destroyed by a magazine explosion.
Persano broke off the engagement, and though his ships still outnumbered the Austrians, Persano refused to counter-attack with his badly demoralized forces.
In addition, the fleet was low on coal and ammunition.
The Italian fleet began to withdraw, followed by the Austrians; as night began to fall, the opposing fleets disengaged completely, heading for Ancona and Pola, respectively.
Re di Portogallo emerged from the battle relatively unscathed, though many of her iron plates had been loosened in the collision with Kaiser.
On 16 July, Persano took the Italian fleet out of Ancona, bound for Lissa, where they arrived on the 18th. With them, they brought troop transports carrying 3,000 soldiers; the Italian warships began bombarding the Austrian forts on the island, with the intention of landing the soldiers once the fortresses had been silenced. In response, the Austrian Navy sent the fleet under Tegetthoff to attack the Italian ships. Re di Portogallo was at that time in the 3rd Division, along with the ironclads Terribile, Formidabile, and Regina Maria Pia, and the coastal defense ship  Varese. After spending the 18th unsuccessfully bombarding the Austrian fortresses, the Italians withdrew late in the day, preparing to launch another attack the following morning.  Persano sent most of his ships to bombard the town of Vis, but he was unable to effect the landing.
The next morning, Persano ordered another attack; four ironclads would force the harbor defenses at Vis while Re di Portogallo and the rest of the fleet would attempt to suppress the outer fortifications. This second attack also proved to be a failure, but Persano decided to make a third attempt the next day. Re di Portogallo and the bulk of the fleet would again try to disable the outer forts in preparation for the landing. Before the Italians could begin the attack, the dispatch boat Esploratore arrived, bringing news of Tegetthoff's approach. Persano's fleet was in disarray; the three ships of Admiral Giovanni Vacca's 1st Division were three miles to the northeast from Persano's main force, and three other ironclads were further away to the west. Persano immediately ordered his ships to form up with Vacca's, first in line abreast formation, and then in line ahead formation. Re di Portogallo initially had trouble getting her engines running, but after repairs were quickly made, she joined the rest of the fleet. She was one of the last ships in the line.
Shortly before the action began, Persano decided to leave his flagship and transfer to Affondatore, though none of his subordinates on the other ships were aware of the change. They were thus left to fight as individuals without direction. More dangerously, by stopping Re d'Italia, he allowed a significant gap to open up between Vacca's three ships and the rest of the fleet. Tegetthoff took his fleet through the gap between Vacca's and Persano's ships, in an attempt to split the Italian line and initiate a melee. He failed to ram any Italian vessels on the first pass, so he turned back toward Persano's ships, and took Re d'Italia, San Martino, and Palestro under heavy fire. The Austrians quickly inflicted serious damage on Re d'Italia and Palestro, eventually sinking both ships. After Palestro withdrew, the Austrian ironclads turned their attention to the 3rd Division, including Re di Portogallo.
Re di Portogallo initially attacked the unarmored ships Erzherzog Friedrich and Kaiserin Elizabeth before the ship of the line Kaiser rammed Re di Portogallo in an attempt to save them. Kaiser struck only a glancing blow, however, and inflicted little damage. Re di Portogallo fired her light guns into the ship in response, starting a fire, and killing or wounding a number of Austrian gunners before Kaiser could break free. By this time, Re d'Italia had been rammed and sunk, and Palestro had been set on fire, soon to be destroyed by a magazine explosion. Persano broke off the engagement, and though his ships still outnumbered the Austrians, Persano refused to counter-attack with his badly demoralized forces. In addition, the fleet was low on coal and ammunition. The Italian fleet began to withdraw, followed by the Austrians; as night began to fall, the opposing fleets disengaged completely, heading for Ancona and Pola, respectively. Re di Portogallo emerged from the battle relatively unscathed, though many of her iron plates had been loosened in the collision with Kaiser.
Italian ironclad Re di Portogallo