JustGiving was the fundraising partner for the marathon between 2012 and 2017, with Virgin taking over for the 2018 and 2019 events.
But after Virgin decided against continuing its relationship with the marathon, JustGiving has returned as the fundraising partner for the race.
This year’s event, which took place on Sunday, raised more than £6m for good causes and saw 18,000 people take part.
Entry for the 2020 marathon opens this week.
Keith Williams, general manager and head of UK at JustGiving, said: "It’s fantastic news that the Brighton Marathon has returned to JustGiving and chosen us as its preferred fundraising partner.
"The Brighton Marathon is known for being a destination event creating life-changing experiences for people and making a big ‘for-good’ impact in the world while doing it, which makes this partnership even more aligned in combined missions."
Tom Naylor, director of Brighton Marathon Weekend, said that JustGiving’s recent decision to remove its 5 per cent platform fee was an important factor in why it was chosen to partner the event.
"We’re so excited to be partnering with JustGiving again for the 2020 Brighton Marathon Weekend," Naylor said. "Our event participants deserve the best fundraising experience and JustGiving is the platform to deliver this.
"Brighton Marathon’s goal is to continue to innovate and break fundraising records, and working with the JustGiving team will help us to achieve this."
A statement from Virgin Money Giving said: "Virgin Money Giving has made the decision to end its partnership as the official fundraising partner of the Brighton Marathon following this year’s race.
"This decision is for commercial reasons and has no bearing on our fundraising partnership arrangements for other events.
"We wish the Brighton Marathon every success moving forward."