The retired mail carrier from Ahuntsic has been a candidate for the party in the Crémazie riding for the past three provincial elections.
Québec Solidaire's policy is to have two spokespeople — one male and one female.
Frappier is replacing Amir Khadir, who stepped down from his role as parliamentary spokesperson last month.
Frappier will serve as co-spokesperson until party delegates elect an official successor in May 2013. The successor will then serve for a two-year term.
Frappier has been active in various labour unions over the past 30 years, including the Canadian Union of Postal Workers (CUPW) and the Greater Montreal FTQ Regional Council.