The blaze, blamed on an electrical overload, broke out just after 6:00 am (0300 GMT) Saturday at the apartment where three families lived in central Riyadh, Philippines charge d'affaires Iric Arribas told AFP.
All three family members, including the 18-month-old daughter, died from smoke inhalation, he said.
The father of a second family had just left for work when the building caretaker called to alert him to the blaze. He rushed home to find that his wife, son and daughter were all dead, Arribas said.
Filipinos are one of the major expatriate communities in Saudi Arabia, working in a range of jobs from hospitality to nursing, labour, and management.