He graduated from Bishop Ryan Catholic Secondary School and then attended McMaster University, earning a Bachelor of Arts degree in economics.

In 2004, the decennial redistribution process took place and Valeri's old riding of Stoney Creek, which straddled the border between Hamilton and Grimsby, was split in two.

He therefore decided to run in the western half of his former riding, resulting in a passionate nomination battle with former cabinet heavyweight and party leadership candidate Sheila Copps.

Stelco's economic troubles and the large pension deficit galvanized support for New Democratic Party (NDP) candidate Tony DePaulo in Hamilton East—Stoney Creek.

The conflict with Copps, public reaction to the first budget of the Ontario Liberals, as well as the government's sinking fortunes, almost cost him his seat, but he was narrowly (less than 1,000 votes) re-elected on June 28, 2004.

In his 2008 memoir, entitled Hell Or High Water: My Life In And Out of Politics (ISBN 0771056923), former Prime Minister Paul Martin labeled Valeri as “one of the most gifted House Leaders of recent times.” On January 23, 2006, Valeri was narrowly defeated by a margin of less than 500 votes by the New Democratic Party candidate Wayne Marston.