Siniša Ostoić is a long-term director of SEHA d.o.o., which manages the SEHA-Gazprom League, South East Handball Association League. After finishing his professional playing career, he began his work on projects related to management in sports, including handball. Siniša is a well-known and recognized personality in the handball world. Since 2007, he has been working within the Organizing Committee for the 2009 World Handball Championship. He has also played one of the main roles in almost all major handball competitions organized in Croatia: 2014 European Women's Handball Championship, 2018 European Men´s Handball Championship and many others. Apart from Croatia, Siniša also has many years of experience working in the Middle East, where he has lived in Iran, Bahrain, Oman and Qatar. After returning to Croatia, he took over the managerial position at SEHA, where he is still a successful director.

SEHA Final 4, a handball spectacle, whose director is Siniša, is a multiple winner of awards for the best sports event in the Adria/Balkan region by various sports festivals and congresses. In addition to all the above, in his rich biography, Siniša also has a position in the Beach Handball Commission, within the European Handball Federation, which he held from 2012 to 2015. It should be noted that Siniša is a multiple world and European champion in beach handball, as well as a great enthusiast about his job who is constantly living and working hard.