Iglesias, 35, has been dating his tennis star girlfriend Anna Kournikova, 29, for the past nine years but said he still has no plans to get married to her.
He said to UK magazine Closer: "I think marriage is great but personally, I don't think it makes a lot of difference. It's too much of a commitment.
"Relationships are difficult - they're great when everything is going well but they're a lot of work too."
He admitted that Anna is his first serious girlfriend.
Iglesias added: "I never said the term 'girlfriend' with ease before her. It's a matter of trust. She's the only serious girlfriend I've had."