The attack happened around 3.15 am at a house in Austin Drive, Tandragee.
The petrol bomb was thrown at the front of the house.
Local fire fighters were called to put out the blaze.
A man in his 30s and a woman in her 20s who were in the house at the time were fortunate not to be injured.
The kitchen in the house was smoke damaged.
Detectives in Armagh are trying to establish a motive for the attack.
Anyone who witnessed the incident or knows who was behind it is asked to contact detectives in Armagh on the 101 number.