The main race was due to take place on April 19.
But since the spread of the new virus, which has prompted the postponement of many sporting events, including the Premier League, it appeared unlikely it would be held then.
Now, organisers of the event have decided to postpone the event until later in the year.
A statement from Tom Naylor, event director, said: "Following the escalation of coronavirus, we have been taking advice from official bodies, while also working closely with other mass event organisers to understand the situation for the industry, our participants and supporters.
"It is with heavy hearts that we have to deliver the disappointing news that the Brighton Marathon Weekend has been postponed until Friday 18th September – Sunday 20th September 2020.
"It is a decision that has not been taken lightly by our team or our colleagues in the running events industry. We as organisers now face considerable challenges as a result.
"We apologise profusely to anyone affected by this postponement."
The Brighton Marathon, BM10k and BM Ride will all take place on Sunday, September 20.
All those who had a place at this year's event can use their place in the rescheduled event or defer it until 2021 if they cannot make it in September.
Mr Naylor said more information about the postponement would be given on Monday, March 16, and urged people to wait until then before contacting the customer services team, who were 'under much pressure at this time'.
He went on to say: "We wholeheartedly appreciate the far reaching impact this change will have on the thousands of you who have trained hard and planned extensively to take part in April 2020.
"Also to all those who have worked tirelessly to fundraise for their chosen charities and how this may impact upon your charity or cause. We hope that you can continue with your Brighton Marathon Weekend journey and implore you to keep on fundraising until the event can take place in September.
"Thank you to Brighton & Hove City Council, our contractors and partners for their cooperation and understanding."
Last week, the World Health Organization declared coronavirus to be a pandemic. The last figures suggest that more than 125,000 people have been diagnosed in 118 countries, and deaths total more than 4,600.
Four cases have been diagnosed in West Sussex, nine in Brighton and Hove, and East Sussex has had its first confirmed case yesterday (March 13).