Over the last months, as oncology specialists, we have frequently been contacted for estimating prognosis for cancer patients affected by COVID-19 infection. Until now, there have been no clear markers to guide decision making regarding the appropriateness of invasive ventilation in cancer patients affected by COVID-19 infection. We developed a practical tool encompassing a prognostic score, “The Milano Policlinico ONCOVID-ICU score.” The score is composed of three groups of variables: patient’s characteristics such as sex, age, BMI, and comorbidities; oncological variables (treatment intent, life expectancy, on or off-treatment status); and clinical parameters in association with laboratory values (the Sequential Organ Failure Assessment (SOFA) score and D-dimer). The SOFA score includes six different clinical parameters and during the first few days of ICU admissions has an important prognostic role. The oncological history should never represent, per se, a contraindication to intensive care and must be considered together with other variables, such as laboratory values, clinical parameters, and patient characteristics, in order to make the hardest but best possible choice. To our knowledge, “The Milano Policlinico ONCOVID-ICU score” is the first prognostic score proposed in this setting of patients and requires further validation. This tool may be useful to assess the prognosis of cancer patients in critical conditions.