The ad – which is not the first gay-friendly campaign the company has run – shows two men holding hands under the slogan: “We are open to all families.”
Below, text says: “With us you will feel at home. What we want to do is make life easier for everyone, every family, every couple, whoever they are.”
Italian newspaper Il Giornale, which is owned by prime minister Silvio Berlusconi, accused IKEA of “Swedish imperialism” and trying to be “provocative”.
Mr Berslusconi said this month that his government would never allow gay couples to marry or adopt children.
But the Queer Italy blog welcomed the ad, saying: “Nothing can be more indigestible for our bigots and homophobes who cannot bear to read the word family with the words same sex.
“We like this advert and we welcome it – maybe some others will follow on from this campaign and look forward progressively and modernly, instead of backwards to the Middle Ages.”
In the past, IKEA has had to withdraw gay-friendly adverts. Its first gay ad, in 1994, showed a gay male couple shopping for dining tables. It was pulled after the retailer received a bomb threat.
In 2008, Polish Catholics called for a boycott of IKEA because its catalogue featured gay couples. The store was accused of “promoting” homosexuality.