The airstrike was launched in retaliation to the US drone strike which killed Iran’s most powerful general Qassem Soleimani.
Donald Trump had said no Americans were harmed after the strike, on Ain al-Asad airbase but the number has been raised by the Pentagon three times.
Lieutenant Colonel Thomas Campbell, a Pentagon spokesman, said there were 16 additional service members diagnosed with an injury, taking the new total to 50 from the 34 announced last week.
Of those 50, 31 have returned to duty.
The injuries can be varying degrees of concussion, impairment of thinking, memory, vision, and hearing. Severity and duration of the injuries can vary widely and they have become a bigger concern for military in recent years.
The chief Pentagon spokesman, Jonathan Hoffman, said last week that a lot of TBI symptoms develop late and manifest themselves over time.
On Friday, he said: “The symptoms can get better. They can get worse.
“So we may see those numbers change a little bit. This is a snapshot in time.”
Last week, another Pentagon spokesman said eight US service members who were sent to Germany were then taken to the United States.
After the Pentagon reported on 17 January that service members had been taken out of Iraq with concussion like symptoms, Mr Trump said: “I heard they had headaches and a couple of other things … and I can report it is not very serious.”
But William Schmitz, national commander of the Veterans of Foreign Wars, said on Friday he “expects an apology from the president to our service men and women for his misguided remarks”.
Many of the soldiers were in bunkers before nearly a dozen Iranian missiles exploded in the attack.
The attack on the US airbase has so far been the end of military escalation between the two sides.
