There are several ways to get Croatian citizenship for a person born abroad. First,  you automatically qualify if at least one of your parents is a Croatian citizen. That’s qualified by at least one of your parents being born on the territory of the Republic of Croatia (which counts for anyone born in Croatia during Yugoslavia too) or if one of your parents was born in a different part of Yugoslavia but declared “Croat” as their ethnicity. People born in Bosnia and Herzegovina to at least one Croat parent are automatically considered natural born Croatian citizens. 

You have to be 18 years old or older. You can get Croatian citizenship through marriage to a Croatian citizen. If you meet none of the prior criteria then you can submit an application for the Naturalization process. Naturalization includes 5 years permanent residence on Croatian territory, 18 years of age minimum, adequate knowledge of the Croatian language and written Latin script, haven’t got in trouble with the law. Croatia recognizes dual citizenship.