After missing the second half of the last World Cup campaign with a rib stress fracture, the Swede has been testing herself out on the shooting range during her recovery.
"I believe that the routine of the rifle and learning all about the weapon will be the biggest challenge. But it's a challenge I'm looking forward to." - Stina Nilsson to FIS Ski
Nilsson also posted a video to her fans on Instagram in which she admitted she is "really a beginner" but that her new experience has been "incredibly fun".
Stina Nilsson - cross country star turned biathlon novice
Nilsson quits cross country skiing as one of the top athletes of her generation.
With 23 wins out of 41 podium finishes from 108 World Cup starts, the 26-year-old suffered a rib injury in the first leg of the Tour de Ski which was later diagnosed as a stress fracture necessitating six months rest.
While sprinting was clearly her favoured discipline, she showed she could mix it with the best over longer distances with bronze in the 30km Classical mass start in PyeongChang, and victory over Therese Johaug in the Quebec World Cup 10km mass start last March.
Now Nilsson has to start from scratch in biathlon with the Swedish Biathlon Association reportedly excited by her move.
She told fis-ski.com, "My plan was to continue cross country skiing for another Olympics and then switch after 2022.
"But because of my injury I have had a lot of time to think and test shoot, and I feel that I really don't want to wait any longer."
Nilsson has indicated that she still wants compete in cross country at a lower level, adding, "I would like to see cross country skiing and Biathlon go a bit hand in hand for me. My ambition is to be able to appear as a guest for my ski club IFK Mora on relay teams in the future."
While switching from cross-country skiing to biathlon is rare, Nilsson will be hoping to follow the lead of Anfisa Reztsova.
Competing initially for the Soviet Union at Calgary 1988, Reztsova won 4x5km relay gold and 20km freestyle silver in cross country.
Four years later in Albertville, she competed in biathlon for the Unified Team and her 7.5km sprint triumph saw her become the only athlete to claim golds in both disciplines.
She won her third Olympic gold, this time for Russia, in the 4x7.5km biathlon relay at Lillehammer 1994.
Reztsova returned to cross-country after giving birth to her second child and was part of Russia's victorious 4x5km relay team at the 1999 World Championships.