At least two men were seen throwing the improvised flammable devices into a home in Hudson Road, South Granville, about 10.30pm (AEDT) on Wednesday.
Four people, some of whom are known to police, escaped injury when the bottled devices ignited a small fire.
"I wouldn't say it was a professional job, but it was certainly a bad thing and we'd hate to see it repeated anywhere," Deputy Police Commissioner Nick Kaldas told reporters on Thursday.
"It could have had very serious ramifications if the fire had caught alight and perhaps the whole dwelling burnt down."
Firefighters quickly extinguished a small fire at the home and witnesses have told police they saw two men throw Molotov cocktails before fleeing on foot.
"There's a very strong lead being followed and some of the people involved are known to us," Mr Kaldas said.
Police have not linked the attack to the spate of shootings across Sydney in recent weeks.