The 84-year-old , and a 44 year old man, had escaped the engulfed two-storey Gold Coast home via the garage after they attempted to rescue a fellow resident on Wednesday.
The two men were critically injured when they tried to break into a locked bedroom and save the person inside but were forced to retreat from the flames.
The body of a 38 year old man - who is yet to be formally identified - was discovered in the bedroom after firefighting crews took almost two hours to extinguish the fire at the Hope Island home.
The 84 year old and 44 year old were rushed to hospital with burns to their head, neck, chest, back, arms and legs.
However, police confirmed on Thursday morning that the older man - who suffered burns to 50 cent of his body - had succumbed to his injuries in a Brisbane hospital on Wednesday.
The 44-year-old - who suffered burns to 40 per cent of his body - remains in a critical condition, police said.
Two other people - a 59-year-old woman and a 38-year-old man - escaped the blaze by jumping off an upper level balcony.
The woman remains in hospital after suffering a back injury while fleeing the house.
The badly damaged house was declared a crime scene, but the cause of the fire was still unknown, police said on Wednesday.
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