Police say they were called to a disturbance at a residence in Wallaceburg around 3:30 a.m. Friday.
Officials learned a verbal argument had gotten physical, and the younger brother reportedly assaulted his older brother with a kitchen knife.
The 18-year-old victim was taken to hospital with non-life-threatening injuries.
The 16-year-old youth fled the scene before police arrived, but police say he was found a short time later and was taken into custody.
The youth has been charged with assault causing bodily harm and being in possession of a weapon for a dangerous purpose.
He was also arrested on an outstanding warrant for break and enter.
The youth remains in police custody.