Toni Iwobi announced “with great emotion” he had been elected in Brescia, Lombardy, to the upper house of the country’s parliament.
The far-right League became the second-largest party in parliament in Italy’s general election.
In a Facebook post, Mr Iwobi said: “After more than 25 years of battles as part of the League’s great family, I am about to start another great adventure!”
The League’s economics chief cited Mr Iwobi’s election as evidence the party was not racist.
“I’d like to point out that the first black senator in the history of the Italian republic is one of ours,” Claudio Borghi told Reuters.
His comments came after hundreds of African immigrants and Italians protested in Florence for a second day, chanting “no more racism” and criticising the anti-immigrant party for stoking racial tensions after an Italian man shot dead a Senegalese street vendor.
Italian politicians, especially those from the League, regularly portrayed migrants as criminals and called for mass deportations during the country's parliamentary election.
Last month, a man with neo-Nazi sympathies and ties to the League opened fire on African migrants in the city of Macerata, wounding six before he was captured.
On Tuesday, protesters targeted the League’s leader, Matteo Salvini, singing: “Salvini vaffanculo (f*** off).”
Mr Iwobi, the party’s spokesman on immigration, has been a League member for 25 years.
He helped write the party’s anti-immigrant platform, which proposed measures to make it easier to deport migrants and to refuse to take in refugees rescued by NGOs in the Mediterranean.
Mr Iwobi has insisted the party is not racist.
“Racism means feeling superior to others. While in the movement I find many strong positions, but also a lot of respect,” he told the newspaper Corriere della Sera.
More than 600,000 migrants have arrived on Italian shores over the past four years, making immigration a top concern for voters during the campaign.
The League and the Five Star Movement, which emerged as the largest party in the vote, have both promised to ramp up deportations of illegal migrants.
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