"My motivation is unstoppable, you know that, and I feel that it (biathlon) is just as much fun today - I would have liked to have had another year, but this is my last season," Bjoerndalen told a news conference as he struggled to hold back the tears.
Known in Norway as "the King of Biathlon", Bjoerndalen thanked his family and the Norwegian people and revealed that he had experienced several episodes of heart palpitations over the last year.
"I responded well (to treatment) and I got very good help form my medical team, but I was always trying to catch up," he said of his final season in which he finished 43rd in the World Cup and missed out on selection for the Pyeongchang Olympics.
Boe wins third consecutive overall biathlon World Cup
Bjoerndalen, 44, won 13 Olympics medals and was the most successful winter Olympian of all time until Norwegian cross-country skier Marit Bjoergen broke his record by taking her tally to 15 in Pyeongchang.
Widely regarded as one of Norway's greatest athletes, Bjoerndalen married Belarusian biathlete and 2018 Olympic relay gold medallist Darya Domracheva in 2016.
He plans to take some time out before deciding what to do next.
Boe claims final day spoils for second season running
Simon Desthieux wins mass start race in Ostersund