Segecic's first statement regarding his allegiance switch comes as talented attacker Daniel Bennie expressed his interest in playing for either Australia or Scotland.
Football Australia and Socceroos staff were blindsided when the Croatian federation informed them Portsmouth and former Sydney FC attacker Segecic had applied to change associations, which officially went through on Friday.
Tony Popovic and his staff had been monitoring the 21-year-old, who was called up last September but didn't debut, until that point.
"It wasn't easy to make this decision because I grew up in Australia, which I represented at youth levels, so I would like to express my gratitude to the coaches and teammates with whom I shared the dressing room," Segecic told the Croatian football federation's website.
"However, my family is from Croatia and I feel a connection to the Croatian people. I felt the desire to represent Croatia as my homeland.Â
"I thank the Croatian Football Federation for their dedication during this process - I clearly felt the desire from people in the Federation for me to become part of the Croatian football family.
"I will continue to work hard to fulfil my football dream of playing for the senior Croatian national team."
Segecic won't link up with Croatia's world No.11-ranked senior team straight away, instead initially joining the U21s for their European qualifiers.
Croatia football director Stipe Pletikosa believed Segecic's talent had a place in the senior team.
Elsewhere, former Perth Glory young gun Bennie, 19, is thriving at QPR and looms as a potential future Socceroo, having played U17s and U20s for Australia.
The winger was born in Hong Kong to Scottish parents and indicated his potential interest in representing Scotland, who are back on the World Cup stage this year.
"I'm really proud of both my Australian and Scottish roots. So whatever happens, whoever comes, whoever believes in me, I'll be proud to represent them," Bennie told The Times.
"I know some people might think I'm only interested (in Scotland) because of the World Cup, but this is something I've had in my head for as long as I can remember."
Bennie said he had spoken to former QPR teammate Lyndon Dykes, who opted to represent Scotland despite growing up on the Gold Coast.
Popovic has made it clear he won't be "selling the shirt" to dual-nationality prospects.
The Socceroos are still awaiting a decision from Italy youth international Cristian Volpato, who has warmed to the idea of playing for Australia and met with Popovic and assistant Paul Okon in Italy last month.
Popovic meanwhile has some players in goal-scoring form ahead of friendlies against Cameroon and Curacao this month.
Nestory Irankunda, Alex Robertson and uncapped strikers Deni Juric and Tete Yengi all scored on Saturday.
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