In January 2006, Genoa signed Forestieri on a three-year contract. Boca tried to keep the young player, but failed to do so. In March, Boca contested the regularity of the transfer and, refusing a €300,000 indemnification from Genoa, the Argentine club submitted the case to the AFA. That summer he played some friendly matches with Genoa, and in one of them Torino president Urbano Cairo saw Forestieri in action and offered €500,000 for him, but Genoa refused.
On 8 November 2006, Forestieri made his official debut with Genoa in a Coppa Italia loss against Empoli. Forestieri made his Serie B league debut on 13 January 2007, on an away match lost 2–1 to Pescara, by scoring for Genoa. He then played as a regular with the Genoa Primavera youth team that won the 2007 International Viareggio trophy.