The men, aged 18 and 21, were arrested following the attack at the party on Henry Lawson Drive in East Hills in the early hours of Sunday morning.

Police said the two gatecrashers turned up at the home and the younger man began arguing with an 18-year-old man, who was believed to have been hosting the party with a friend.

A NSW Police spokeswoman said the two gatecrashers then left the party, before returning about 4.45am allegedly armed with a golf club.

The 18-year-old gatecrasher allegedly struck the other 18-year-old in the face with a glass bottle, which shattered.

When the injured man's 19-year-old friend tried to intervene, he was allegedly assaulted a number of times by the two men, before they fled.

Police and paramedics were called, and the injured 18-year-old was taken to Bankstown Hospital where he was treated for cuts to his face.

His 19-year-old friend was treated by paramedics and did not require further treatment.

Police interviewed a number of guests at the party.

At 7.40pm on Sunday, police arrested an 18-year-old man and a 21-year-old man at a home on Lehn Road in East Hills.

They were taken to Bankstown police station, where the younger man was charged with wounding a person with intent to cause grievous bodily harm, two counts of assault occasioning actual bodily harm, and common assault.

The older man was charged with two counts of assault occasioning actual bodily harm, and being armed with intent to commit an indictable offence.

Both men were refused police bail and are due to appear at Bankstown Local Court on Monday.