Almost 58% of Croatians plan to vote for EU membership against 23% who oppose it, according to a survey released two weeks before a referendum on the subject.
More than 60% of the 1,300 people questioned in a poll by the Promocija Plus agency said they would definitely vote in the referendum.
11% said they would probably go out to cast their ballot, according to a national television report on the results.
Croatians will vote on 22 January in a referendum on EU entry.
The former Yugoslav Republic, independent since 1991, signed the EU accession treaty in December.
The move paved the way for it to join the bloc on 1 July, 2013.
The treaty also has to be ratified by all current 27 member states.