Sascha Hüsges was badly injured when he rushed to help victims of the 2016 Christmas market attack in Berlin. Five years on he has become the 13th to die.
He was apparently hit on the head by a beam and needed 24-hour care ever since. His partner said he died of infection related to long-term illness.
Tunisian Anis Amri, who was a known jihadist threat, drove a lorry into the crowded market on Breitscheidplatz.
He fled to Italy and was shot dead by police in Milan four days later.
Amri, a failed asylum seeker, initially shot dead the lorry driver on 19 December 2016, before ploughing the vehicle into the Christmas market.
Eleven people died at the market at the time and many more were wounded. A report the following year, ordered by Berlin's state senate, found that surveillance of Amri had been dropped even though police had been warned he was a potentially violent Islamist.
Sascha Hüsges, 49, was among the first on the scene of the attack to help the wounded.