The agency will also focus on communicating the brand’s work on farmland biodiversity.
Jordan's head of brand David Towse said Greenhouse was an agency that aligned with the brand’s values.
"We have some really exciting plans in the pipeline for 2020 and are looking forward to working with the Greenhouse team to amplify our efforts to boost biodiversity," he added.
Greenhouse director Helen Bell said: "Jordans Cereals is an iconic British brand with a strong heritage and track record of conserving nature. We’re excited to be partnering with them in 2020 to champion biodiversity and help consumers better understand how important it is and what they can do to help.
"We face a major tipping point and need more purpose-led brands like Jordans to lead the way in driving positive social and environmental change."
Greenhouse said it has won more than £500,000 worth of new business in the past six weeks and has expanded its team from 18 to 30 people. The agency has offices in London and Bristol.