The Institute of Cancer Research's (ICR) first phase of Sutton for Life is the Centre for Cancer Imaging, which will assess new cancer drugs.
Plans for the site also include a new school offering apprenticeships in life sciences at the centre.
ICR said the project could eventually create up to 10,000 new jobs.
Sutton Council said, when complete, the cancer research campus would be second only in size globally to the MD Anderson campus in Texas, United States.
The newly-opened Cancer Imaging Centre allows researchers to assess and monitor the effectiveness of cancer drugs as well as develop new imaging techniques to view tumours.
Cathy Scivier, ICR's chief operating officer, said: "Our long-term plan for this site is to create a second town centre for Sutton which includes coffee shops and a crèche."
Ms Scivier said the estimated investment for the project did not include the costs of any new transport infrastructure, which includes a proposal to extend a tram link up to the site.
Researchers are expected to move into the cancer imaging centre over the next few months.
The first phase of a £170m project to build the UK's biggest campus specialising in cancer diagnosis is complete in south west London.