The 61-year-old politician has represented Vancouver East since 1997.
Long before she was an MP, Davies was a Vancouver councillor and activist in the city's Downtown Eastside, which later became her federal riding.
Davies told reporters Friday that after almost 40 years in public service, it was time for her to pass the torch.
She has served as NDP house leader and deputy leader in Parliament.
Davies says over the years she's taken on tough issues like the need for drug-policy reform, even after hearing she wouldn't be re-elected for doing that.