The initial contract includes two one-year options.
A Geoscience Australia spokeswoman told Australia's Mining Monthly Cirrus would provide comprehensive information, communications and technology services support and management services.
She said that included core workplace services, network services, infrastructure operations and ICT security services for the organisation.
Other activities to be provided under the contract scope include service desk, device and application management, tech bar support, training and enrichment.
Cirrus will also provide ICT security services across GA's ICT environment as well as infrastructure operations, which includes management, support, configuration and monitoring of GA's data centres.
It is taking over from current provider DXC Technology, with work to start straight away.
The final handover will be in May.
Cirrus managing director Matt Sullivan said the contract provided great confidence that the service focused strategy was succeeding and the goal of being the managed service provider of choice to mid-tier government agencies and corporates was in sight.
"We look forward to this contract providing great outcomes for Geoscience Australia and being a springboard for further contract success within similar clients nationally," he said.
Sullivan said the contract success represented a transformational win for the Canberra office and its managed service business unit.
"This success is a key win for Cirrus and presents the company an opportunity to demonstrate its benchmark outsourcing methodology to Geoscience Australia, creating value while providing a reference point for other federal and state government organisations," he said.