Logan Porter, 24, was teaching social sciences at the American Academy in the Slovakian capital of Bratislava, having started his job at the English language-school in September.
His devastated family do not yet know the circumstances of the former Barnsley College student's death and have struggled to obtain further details from Slovakian authorities.
He was found collapsed in his home.
Logan, from Worsborough Common, had been due to come home for Christmas on Friday at the end of his first term, and had recently been visited in Bratislava by his girlfriend Nardine Michaelis during the half-term break.
He studied history at York St John University, before completing a Masters in social history at Leeds Beckett University. He then took a PGCE course at Sheffield Hallam University to qualify as a teacher.
Logan's sister Camilla Porter said:-
"It was a complete shock for us, completely out of the blue. We have no idea what happened yet, we are still waiting on the cause of death from postmortem results."
The family's Gofundme appeal has so far raised over £7,000 towards the £10,000 needed to fly Logan's body back to the UK for burial.
"My amazing, kind, daft brother Logan has passed away. Logan was living his best life, teaching in Slovakia, and surrounded by love and laughter. He thought the absolute world of his students, and we are grateful and thankful he had found a career and place to work that he enjoyed and thrived in. As a family we need to personally cover the repatriation costs which could be anything up to £10,000 before the costs of the funeral itself."
Donating to the fund, Logan's former university tutor Andy Bull commented:-
"Logan was one of my students on the PGCE history course at Sheffield Hallam in 2017/18. I saw him teach on two occasions, and as well as being a real enthusiast for our subject, it was obvious that he cared deeply about the pupils in his care and he formed a real rapport with them. Like many students, Logan had to work hard to get through tough times on the course. He was determined and resilient, this was something he wanted to achieve and he got there with flying colours. We exchanged emails recently, and it was obvious that Logan was enjoying his time teaching overseas, and it was so pleasing to hear. He was a really promising young teacher, and a sad loss to the future of the profession. He'll be very fondly remembered by all the staff who worked with him, and by his fellow students. As well as being a great teacher, Logan was a lovely, warm person with a great smile and sense of humour. I'm so sad that we've lost him."
Logan used to work at the Primark store in Barnsley, and former colleagues have donated to the appeal as well as Slovakian families whose children he taught.
He had taught at schools in Barnsley but decided to look for posts abroad as he had become disillusioned by pupil behaviour. He had planned to stay at the international school for two years.