Jerome Kennedy resigned Wednesday to return to working as a lawyer starting at the beginning of next month.
Dunderdale wouldn't say if she'll call the byelection before the Liberal leadership convention in November.
Kennedy leaves behind a six-year tenure in public life that saw him preside over several of the majority Progressive Conservative government's top cabinet posts.
He says he decided over the summer to leave politics.
Dunderdale is expected to shuffle her cabinet before Oct. 15.
(VOCM, The Canadian Press)