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.
Two more Americans have been confirmed as having died in the Brussels terror attacks, bringing the total number to four.
The US State Department confirmed the deaths but did not identify the victims.
"We can confirm the deaths of two additional US citizens in Brussels, and we express our deepest condolences to their loved ones," a State Department official said.
"We have no further information to share out of respect for the families during this difficult time."
American couple Justin and Stephanie Shults were confirmed dead by an employer and family on Saturday.
Tuesday's attacks on the Brussels airport and metro system killed 31 people and injured many more.
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.