Sheila Malcolmson from NDP won Nanaim's choice, retaining delicate party power, CBC News projects.
Malcolmson, a former federal representative of the NDP, will replace Leonard Kro, a five-year member of parliament who resigned last year after being elected mayor of Nanaimo.
The election results on Vancouver Island retained the status quo, with opposition liberals holding 42 seats, only shaken by 43 jointly held by the NDP and the Green Party.
The Greens agreed to support the NDP after the provincial elections in 2017, allowing them to form a minority government.
The NDP held riding, with 45,359 voters registered, for 13 of the last 15 elections. A vote in January means that the winner will sit in the parliament for the winter session and the provincial budget, which will be released in February.