The Mallawa Picnic Races will not be run this weekend.
The committee announced the news on Thursday.
The committee made the decision after a confirmed case of COVID-19 travelled through regional NSW while potentially infectious.
A cafe, tavern, thermal pools and caravan park in Moree are among the venues visited by the case, who NSW Health said drove from Melbourne to the Sunshine Coast in Queensland between June 1 and June 5.
The news on the picnic races comes after the committee had to cancel the 2020 event due to COVID-19.
"Due to the uncertainty surrounding the potential COVID situation in and around Moree at this point, the committee has made the very difficult decision to postpone or cancel the 2021 Mallawa Picnic Races," a statement on the Mallawa Picnic Races Facebook page said.
"This decision was not made lightly, but it has been made to ensure the safety of our members, guests, sponsors and general race goers.
"We apologise for any inconvenience this will cause. For those that have pre-purchased tickets, we are currently working through refunds.
"We would like to acknowledge the very hard work of our committee, and particularly new president, Peter Taunton. We would also like to thank our loyal and dedicated cponsors for their ongoing support.
"This is the second year the pandemic has affected our little race club, but rest assured Mallawa will return bigger and better than ever!"