Background: Differences in genetics and receptor expression (phenotypes) of invasive ductal breast cancer (IDC) impact on prognosis and treatment response. Immunohistochemistry (IHC), the most used technique for IDC phenotyping, has some limitations including its invasiveness. We explored the possibility of contrast-enhanced positron emission tomography magnetic resonance (CE-FDG PET/MR) to discriminate IDC phenotypes. Methods: 21 IDC patients with IHC assessment of oestrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor-2 (HER2), and antigen Ki-67 (Ki67) underwent CE-FDG PET/MR. Magnetic resonance-perfusion biomarkers, apparent diffusion coefficient (ADC), and standard uptake value (SUV) were compared with IHC markers and phenotypes, using a Student's t-test and one-way ANOVA. Results: ER/PR - tumours demonstrated higher Kep(mean) and SUVmax than ER or PR+ tumours. HER2 - tumours displayed higher ADC(mean), Kep(mean), and SUVmax than HER2+tumours. Only ADC(mean) discriminated Ki6714% tumours. PET/MR biomarkers correlated with IHC phenotype in 13 out of 21 patients (62%; P = 0.001). Conclusions: Positron emission tomography magnetic resonance might non-invasively help discriminate IDC phenotypes, helping to optimise individual therapy options.