"It's the Spain of today, but it seems like the Italy of yesterday," Renzi commented in a blog post on his website after the Spanish elections.
"Bless the Italicum (Italian electoral law, which makes forced coalitions impossible), really; there will always be a clear winner and a majority able to govern," said Renzi, referring to the fact that Spanish Prime Minister Mariano Rajoy must now scramble to form a coalition.
Renzi called Spain's result "a vote against austerity." He also said the elections in Spain were "very interesting, because as has already happened in Greece and Portugal, governments which apply rigid austerity measures, even if these are accompanied by positive results, are destined to lose the majority."
The Prime Minister argued that this proved austerity measures "don't help citizens and, paradoxically, punish those who adhere to them."
He added: "Now it will be interesting to find out if Europe realizes that a short-sighted policy of rigour and austerity won't get us anywhere."
Before the exit polls had been announced, Italian MP Maria Elena Boschi, took to Twitter to praise the country's electoral system.
Never has it been as clear as it is this evening how useful and justified our electoral law is
Italian politicians had been paying particularly close attention to the Spanish election because it marked the first national confrontation between radical-left party Podemos and the Spanish Socialist party, or PSOE, as it is known.
On Sunday, Spain's ruling Popular Party won 28.71 percent of the vote, giving it 123 seats in the 350-seat parliament, well short of the 176 seats needed for an absolute majority and down from 186 seats in the outgoing assembly.
Outgoing Spanish Prime Minister Mariano Rajoy, whose party has introduced harsh austerity measures, has said he will try to form a new government.
The Socialists came in second with 90 seats while two newcomers, anti-austerity party Podemos and centre-right Ciudadanos, came third and fourth respectively.