Background: Coronary artery disease (CAD) is a leading global cause of mortality. The role of calcium (Ca), a key metabolic and structural element, in atherosclerosis and inflammation remains unclear. Ca influences immune cell function and is a component of atherosclerotic plaques. Hair analysis reflects long-term mineral exposure and may serve as a non-invasive biomarker. Objectives: This pilot study aimed to investigate the association between hair Ca levels and acute coronary syndrome (ACS), and to evaluate correlations with the Systemic Inflammatory Index (SII), Systemic Inflammatory Response Index (SIRI), and selected CAD risk factors. Methods: Ca levels were measured in hair samples from patients undergoing coronary angiography for suspected myocardial infarction. Associations with ACS diagnosis, Syntax score, SII, SIRI, and CVD risk factors were analyzed. Results: Serum calcium levels were not significantly associated with the presence of acute coronary syndrome (ACS) (p = 0.392) or with its clinical subtypes, including ST-elevation myocardial infarction (STEMI), non-ST-elevation myocardial infarction (NSTEMI), and unstable angina (UA) (p = 0.225). Diagnosis of ACS was linked to higher SII (p = 0.028) but not SIRI (p = 0.779). Ca levels correlated negatively with Syntax score (R = −0.19, p = 0.035) and SII (R = −0.22, p = 0.021) and positively with HDL-C (R = 0.18, p = 0.046). Conclusions: Hair calcium content may reflect subclinical inflammation and CAD severity. Although no direct link to ACS was observed, the associations with SII, HDL-C, and Syntax score suggest a potential diagnostic role which should be further explored in larger, well-controlled studies.