According to the Belga news agency, the decision was taken after an evaluation by the an agency that analyzes threats.
Belgium's authorities have kept the terrorism threat at the second highest tier since March 2016, when a twin terror attack hit the country's capital.
Military patrols in Belgium will remain in place, despite lower terrorist threat level, Prime Minister of Belgium Charles Michel said.
"We will keep the military [patrols] proportionately," Michel told reporters in Brussels.
Starting March 24, 2016, there was an increased, tier 3, level of terrorist threat in Belgium. The tier 4 level was introduced on the day of the terrorist attacks at the airport and metro in Brussels on March 22, and two days later it was lowered to tier 3 notch.