"This is a great shock, which has hit us all very hard," said Thomas Bach, president of the International Olympic Committee (IOC).
"We can hardly believe this terrible news. Particularly since we have seen him working hard, as we always knew him, for the sport he loved.,"
Baumann was born in Basel in Switzerland in 1967 and trained to become a lawyer. His association with the IOC started in earnest in 2007.
Within a decade he was handling high profile assignments. His calm and urbanity were in ample evidence as chairman of the evaluation commission for the award of the 2024 Olympic Games.
With both Paris and Los Angeles vying for the right to stage the event, Baumann presented an image of even handedness.
He was subsequently appointed vice-chair of the coordination commission once Paris was selected to host the event.
He was also president of the IOC's coordination commission for the Youth Olympic Games Lausanne 2020 and the Olympic Games Los Angeles 2028.
"We lose a young and sympathetic leader full of hope who was standing for the future of sport. Our thoughts are with his wife, his children and his family," Bach added.
A former basketball player, coach and referee, Baumann was deputy secretary general between 1995 and 2002 of the International Basketball Federation (Fiba), and then secretary general from 2002.
"Under his leadership, Fiba moved forward by leaps and bounds, with the organisation modernising itself to the extent of becoming a model which fellow international federations followed," said Fiba president Horacio Muratore.
Muratore credited Baumann with helping to promote 3x3 - basketball's urban game featuring only one hoop.
"Without doubt we would not be where we are today were it not for everything that Patrick did," Muratore said.
"His unwavering commitment, tireless work ethic and pure passion for basketball mean he will forever have his place in Fiba's history."