Police said a number of men wearing hooded tops and with their faces covered entered the property on Kinnaird Street around 23.45 pm last night, Saturday, June 4 and attacked the 19-year-old.
The teenager was cut on the neck and sustained bruising to his body.
One of the men was said to have been carrying a gun,.
Several other men remained outside the house during the attack.
The PSNI say that following the brutal assault, the gang made off in the direction of the New Lodge.
A woman in her 40s, who was also in the house at the time, was not injured.
Detectives in north Belfast appealed for anyone with information about the attack to contact them on the non-emergency number 101.