Vrhunsko raziskovalno delo ter razvijanje in uvajanje novih zvrsti zdravljenja lahko poteka le v sodelovanju s priznanimi tujimi onkološkimi centri. Onkološki inštitut sodeluje s tujimi ustanovami v obliki partnerstva ali specifičnega sodelovanja na določenih področjih dela.

V dolgoletnem raziskovalnem delu je Onkološki inštitut sodeloval z naslednjimi tujimi centri: 

• British Columbia Cancer Center, Vancouver
• Centro Riferimento Oncologico, Aviano
• Cork Cancer Research Centre, Cork
• Erasmus University, Rotterdam
• Oxford Insitute for Radiation Oncology, Oxford
• Harlev Hospital, Harlev
• Institut de Pharmacologie et de Biologie Structurale, Toulouse
• Institut Gustave Roussy / CNRS, Villejuif
• Institut Ruđer Bošković, Zagreb
• Klinika za tumore Zagreb, Zagreb
• Istituto Europeo di Oncologia, Milano
• Istituto Nazionale per lo Studio e la Cura dei Tumori, Milano
• Lund University, Lund University Hospital, Faculty of Medicine, Department of Surgery, Lund
• M.D. Anderson Hospital and Tumor Institute, Houston
• Memorial Sloan-Kettering Cancer Center, New York
• National Institutes of Health, Bethesda
• The Netherlands Cancer Institute, Amsterdam
• University of Münster, Münster
• University of Ulm, Ulm

in raziskovalnimi skupinami:

• EORTC - European Organization for Research and Treatment of Cancer
  • EORTC Breast Cancer Group
  • EORTC Gynecological Cancer Group
  • EORTC Lung Cancer Group
  • EORTC Lymphoma Group
  • EORTC Melanoma Group
  • EORTC NOCI
  • EORTC Radiation Oncology Group
  • EORTC PathoBiology Group
• European Network of Cancer Registries - ENCR
• International Agency for Research on Cancer - IARC
• International Breast Cancer Study Group - IBCSG
• Central European Cooperative Oncoloy Group - CECOG
• Central and East European Oncoloy Group - CEEOG
• Breast Cancer International Research Group - BCIRG