David Dixon, 53, who was missing since Tuesday's bombings, has been confirmed dead by his family.
Tuesday's attacks on the Brussels airport and metro system killed 31 people and injured many more.
The Government is "concerned" about the welfare of a British national missing since the Brussels attacks, adding that four Britons were injured in the blasts.
The government did not name the missing Briton, although friends and family have said they have not heard from David Dixon, originally from Hartlepool. He is thought to have been on the metro system at the time of the attacks.
David's partner Charlotte Sutcliffe and other friends say he did not arrive in his office on Tuesday morning in the Belgian capital.
A post on Facebook by Rachel Stevenson said he has not made contact with his partner since leaving for work in the morning.
Britons are now being warned to remain "alert and vigilant" as the Prime Minister said the Government is no longer advising against travel to the Belgian capital.
An American survivor of the Brussels airport bombing - who also survived the Boston bombing - has recounted the deadly attack.
A British woman captured in amateur footage huddling with her family after the Brussels airport blasts has spoken of her ordeal.
After escaping the Brussels Airport suicide attacks, Sneha Mehta wrote an inspirational message of hope and peace for her unborn child.