The money will support the Newlands programme, which aims to turn more than 900ha of brownfield land in the North West into community woodland.
The agency will consider nine new areas for regeneration in the second phase of the scheme. These include Brockholes Quarry near Preston, Hartshead Power Station in Greater Manchester and Huncoat Colliery near Accrington.
As well as regenerating more than 520ha of brownfield land, the extra money will allow Newlands to improve existing regeneration schemes and implement street greening measures.
Forestry Commission regional director Keith Jones explained that Newlands is already helping to uplift the North West.
"The money means that we can now extend the programme to the whole of the region. Before this, it was just two areas," he said.
"We are already seeing benefits in the obvious environmental gains from regenerating brownfield sites in social and economically deprived areas, as well as economic growth."
Total funding for the programme is now worth £59 million and will be used to fund initial regeneration costs as well as 20-year maintenance programmes. Under the deal, the Forestry Commission will manage the sites for 99 years. The second phase will be completed within eight years.