Salvini, who is also deputy prime minister, had a "friendly" conversation with Guaido in which he expressed his "total support" for free elections, later saying they should happen "as soon as possible".
Guaido, who heads Venezuela's opposition-controlled National Assembly, last month declared himself interim president, sparking a standoff with beleaguered President Nicolas Maduro.
He has so far been recognised as Venezuela's interim president by some 50 countries, although Italy is one of the few EU states yet to do so.
During the conversation, Salvini acknowledged Italy's populist government was still divided over the matter even though Rome never recognised Maduro's reelection in May 2018 following a vote which was disputed by the opposition and overseas.
Salvini agreed to see the Venezuelan delegation after Guaido wrote to him requesting that they present him with details of the "action plan to relaunch democracy in Venezuela through free and fair elections".
"I see it as my duty to welcome a delegation from the Venezuelan parliament which is the only legitimate entity in power at this moment given that the apparent president, Maduro, has never been recognised as such by the international community," Salvini said.
The Venezuelan delegation includes a number of senior National Assembly figures such as Francisco Sucre, who heads the parliamentary foreign affairs committee, and Rodrigo Diamanti, its European representative for humanitarian aid.