The rare condition of neutrophils agglutination in-vitro may give inaccurate neutrophils count. We reported a case of a 71-year-old female admitted with a diagnosis of extended-spectrum beta-lactamase (ESBL) Escherichia Coli (E.coli) septicaemia secondary to the left lower limb cellulitis. Despite underlying infection, total white blood cell count (TWBC) and absolute neutrophil count remained in a normal range. An accidental finding of full blood picture (FBP) using K2 ethylenediaminetetraacetic acid (EDTA) tube presented numerous neutrophils agglutination. Further tests were carried out using citrated and heparinised tubes and tested at room temperature, 4 C, and 37 ͦC. The findings showed a significant reduction in neutrophils agglutination in both citrated and heparinised tubes, including when tested at room temperature (RT) and 4 ͦC. Surprisingly, at 37 ͦC, no neutrophil agglutination was observed. This indicates that temperature-dependent anti-neutrophil IgM antibody may be found in the patient's serum that reacted with the EDTA anticoagulant. In conclusion, white blood cells (WBC) agglutination has been associated with malignancy, sepsis, liver disease, and autoimmune disease. Thus, a baseline FBP is recommended, especially in these categories of patients to optimise their clinical management.