The presence of comorbidities has been associated with later stages of breast cancer diagnosis. It is unclear whether biological mechanisms are partly responsible. We examined the association between the presence of pre-existing comorbidities and tumour profile at initial diagnosis with breast cancer. Data for the present analysis were derived from a prior inception cohort study comprising 2,501 multiethnic women, newly diagnosed with breast cancer between 2015 and 2017 in four hospitals across Klang Valley. At the inception of the cohort, medical and drug histories, height, weight and blood pressure were recorded. Blood samples were taken to measure serum lipid and glucose. Modified Charlson Comorbidity Index (CCI) was calculated using data extracted from medical records. The association of CCI as well as specific comorbidities, with pathological breast cancer profile was analysed. Higher comorbidity burden, namely cardiometabolic conditions were associated with unfavourable pathological features including larger tumours, involvement of >9 axillary lymph nodes, distant metastasis and human epidermal growth factor receptor 2 overexpression. These associations remained largely significant following multivariable analyses. Specifically, diabetes mellitus was independently associated with high nodal metastasis burden. Low level of high-density lipoprotein was associated with larger tumours (>5 cm), and distant metastasis. Evidence from this study seems to support the hypothesis that the later stages of breast cancer diagnosis in women with (cardiometabolic) comorbidities may be partially explained by underlying pathophysiological events.