•High SUVmax was significantly related to high TILs in breast cancer patients.•In less aggressive and immune inactive microenvironment such as SUVmax-low, TILs-low, or luminal subtype, SUVmax has an important role in prognosis.•In more aggressive and immune active microenvironment such as SUVmax-high, TILs-high, or HER2-positive and triple-negative, SUVmax has less influence on prognosis. To investigate the relationship between fluorodeoxyglucose (FDG) uptake (maximum standardised uptake value SUVmax) and immune markers (tumour-infiltrating lymphocytes TILs and neutrophil-to-lymphocyte ratio NLR) and evaluate the potential prognostic value of any correlations. Data from 502 patients with breast cancer, including 346 oestrogen receptor (ER)-positive / human epidermal growth factor receptor 2 (HER2)-negative, 88 HER2-positive, and 68 triple-negative cases, who had undergone surgery were reviewed. Relationships between the clinicopathological factors, SUVmax, TILs, NLR, recurrence-free survival (RFS), and overall survival of all patients and each subtype were evaluated using a Cox proportional hazards model and log-rank test. A sub-analysis of patients divided into low and high TIL groups was also undertaken. High SUVmax was significantly related to high TILs (p < 0.0001). In low TIL (TILs1) group, patients with high SUVmax (≥3.585) had a significantly shorter RFS than those with low SUVmax (<3.585; p < 0.0001). In high TIL (TILs2,3) group, patients with high SUVmax had a shorter RFS than those with low SUVmax without a significant difference (p = 0.35). Multivariate analysis of 502 patients showed high SUVmax, high T status, and nodal metastasis were independent negative predictors of RFS. In 317 TILs-low patients, high SUVmax, high T status, nodal metastasis, and ER-positivity were independent predictors of RFS. In 185 TILs-high patients, nodal metastasis was an independent predictor of RFS. In ER-positive/HER2-negative and HER2-positive subtypes, SUVmax was a significant predictive parameter in the TILs-low but not TILs-high groups. FDG uptake may be predictive of immunological features and aggressive features in breast cancer patients.