Background: Inborn errors of immunity (IEI), or primary immune disorders (PIDs), predispose individuals to infections, autoimmunity, inflammation, allergy, and malignancy. Malignancies are a major cause of morbidity and mortality in patients with IEI/PIDs, with poorer outcomes compared with the general population. Objective: We sought to determine the frequency and types of malignancies in patients with IEI/PIDs and to assess clinical management approaches across Europe. Methods: Descriptive analyses were performed on malignancy data within each IEI category. In addition, a European Society for Immunodeficiencies Registry survey (05/2022-03/2024) collected data on management strategies and challenges. Results: Of 19,959 patients with IEI/PIDs, 1783 (8.9%) developed malignancies, of whom 27.1% presented malignancy as first manifestation of IEI/PIDs. A total of 1210 malignancies were specified; B-cell non-Hodgkin lymphoma was most common (24.2%). Detailed malignancy-IEI/PID association maps are provided. Predominantly antibody deficiencies accounted for 59.1% of malignancy cases, with a higher median age at first malignancy (43.6 years) compared with other IEI/PID categories, for example, combined immunodeficiencies with syndromic or associated features (11.7 years). Survey findings revealed that oncological treatment was modified because of IEI/PIDs in 21.5% of cases, with assumed negative impacts of IEI/PIDs on complications and outcomes (in 27.4% and 30.7%, respectively). IEI/PIDs influenced transplant decisions in 16.5% of cases. Management practices such as interdisciplinary decision finding and guideline availability were recorded. Conclusions: This study provides comprehensive epidemiological data on malignancies in IEI/PIDs, highlighting the need for tailored screening and management. Survey results emphasize the real-world challenges and support the development of IEI/PID-specific oncological surveillance guidelines and treatment strategies.