Five members of one St. Vincent household died when a hill collapsed on their house, I-Witness News reported.
A 2-year-old girl, along with her aunt, Kesla James, 18, were also killed when they were washed away by floodwaters.
The National Emergency Management Organization said 50 percent of residents in St. Vincent were without water as a result of the floods.
Eight homes were destroyed and 10 others were damaged, NEMO officials said, but those figures were expected to rise.
In St. Lucia, the victims included a police officer, Calvin Stanley Louis, who died after a wall fell on his while he was trying to assist locals who had become stranded, the Caribbean Media Corp. reported.
The Water and Sewerage Company said the weather has left most of the island without water.