The two environmental charities have previously worked together on UK-wide opportunities including the Tesco plastic bag grant scheme.
The partnership agreement formalises this relationship and will see both charities working closely on the development and delivery of UK-wide programmes relating to community greenspaces.
Both organisations hailed the signing of the agreement, saying it would help communities receive support at a time of significant funding reductions.
Greenspace Scotland chief executive Julie Procter said: "Access to green space makes a big difference to people's lives – making places for children to play, improving health and wellbeing, creating stronger communities and bringing nature into our towns and cities. But across the UK there is still much more to be done to ensure that everyone enjoys the benefits of quality local green spaces."
Procter added: "We're looking forward to the new opportunities this creates for us to work together to share practice across the UK, develop innovative solutions and together deliver UK-wide community greenspace programmes - bringing real benefits to people, places and communities across the UK."
Groundwork UK chief executive Graham Duxbury added: "This strategic partnership adds real value to Groundwork's extensive delivery capability in England, Wales and Northern Ireland, as both charities have a strong track record of working in partnership with communities, businesses and government to improve quality of life through transforming local places and environments.
"By signing this agreement we're committing to working closely to develop innovative solutions to the challenges facing our communities today."