Two years ago, Farah walked away from track events to concentrate on marathons and he finished eighth across 26.2 miles in Chicago last month having won the event in 2018.
However, the 36-year-old has decided to return to shorter distances and will aim to add to his Olympic medal collection at the next Games.
Farah, who will still need to qualify for the event in Tokyo, won gold over 5,000m and 10,000m at the 2012 and 2016 Olympics.
"It's been really exciting to compete at the marathon for the last couple of years," Farah said in a message posted on his YouTube Channel.
"To win the Chicago Marathon, as a major marathon, that was nice. To finish third in the London Marathon, was okay, it was good.
Back to Track!! I will focus on the 10,000m next year at the Olympic Games!! https://t.co/7LQbfSBAcE
— Sir Mo Farah (@Mo_Farah) November 29, 2019
"It's been a good learning curve for me - doing the marathon, to run 2:05 - British record, European record. The training for it was totally different to the track.
"Next year I've decided, Tokyo 2020, I'm going to be back on the track. I'm really excited to be competing back on the track and giving it a go in the 10,000 metres.
"Hopefully I haven't lost my speed. I'll train hard for it and see what I can do."
Photo: Getty Images Caption: Mo Farah