Diane Gregoire was last seen in a mall parking lot south of Montreal in January 2008.
Her remains were found in November after a lengthy investigation.
Gregoire's husband Paul Laplante, a former small-town Quebec mayor, was accused of the killing.
He was found dead in his prison cell earlier this month.
The couple's two children, Elizabeth and Francis, asked for privacy at the funeral in St-Hyacinthe, north of Montreal.