Background: We retrospectively evaluated the correlation between a baseline measurement of CTCs and neutrophils, lymphocytes and platelets levels from peripheral blood along with the neutrophyl-lymphocyte ratio (NLR), platelet lymphocyte ratio (PLR) and systemic immune-inflammation index (SII), as general measures of immune-inflammation status in MBC. Methods: CTCs detection (CTCs+ = ≥ 5CTCs), white blood cell (WBC) counts plus platelet levels, and tumor features of 516 women with MBC before starting a new treatment between July 2002 and June 2009 were recorded at the Department of Breast Medical Oncology, MD Anderson Cancer Center. Counts were log-transformed and effects on these by tumor features and epidemiologic variables assessed by generalized linear models, followed by Cox proportional hazards models to assess effects on overall survival (OS). The optimal predictive value of NLR, PLR and SII to predict survival was determined and compared with CTC < 5 or > 5 per 7.5 ml of blood (CellSeach, Janssen Diagnostics). Results: In the overall population (n = 516), CTCs+ correlated with monocytes (p = 0.008) and neutrophils (p = 0.038). CTCs+ correlated with monocyte count only in triple negative tumors (n = 125), p = 0.009, with neutrophil count in HER2+ tumors (n = 100), p = 0.009, with a trend versus monocyte count, p = 0.061, whereas no correlation was found in HER2- estrogen receptor+ tumors (n = 280). In the overall population, univariate logistic regression analyses of WBC, differential counts, NLR, PLR and SII as a function of CTC ( < 5, ≥ 5) correlated with WBC (OR 1.11, p = 0.006), neutrophils (OR 1.09, p = 0.045) and monocytes (OR 3.75, p = 0.001). In multivariate analysis only monocytes remained associated with CTCs+ (OR 2.72, 95% CI 1.09-6.80, p = 0.033). The following variables predicted OS: CTCs+ (HR 1.82; p < 0.0001), NLR (HR 1.47; p = 0.009), PLR (HR 1.46; p = 0.010), SII (HR 1.34.p = 0.047), respectively. Conclusions: CTC, NLR, PLR, and SII are predictors of OS in MBC. CTC directly correlates with monocytes, in particular in triple negative tumors. Links between CTC and monocytes may provide new clues about the pathogenesis and progression of MBC.