The objective of the study is investigation of serum electrolytes in 16 transient ischemic attack (TIA) and 16 acute ischemic stroke (AIS) patients and analysis of association between these parameters and stroke biomarkers. Materials: 16 healthy volunteers were used as controls. Serum samples were examined for complement components C4 and C3a, vascular endothelial growth factor (VEGF), S100B protein, and NR2 antibodies (NR2Ab). Serum Ca and Mg concentrations were assessed using inductively-coupled plasma mass spectrometry whereas K+, Na+, and Cl- levels were estimated using ion-selective electrodes. Results: TIA and AIS patients were characterized by significantly increased stroke markers in serum. The mean group values of serum electrolytes were within the normal range. At the same time, the level of Cl- in serum of TIA and AIS patients were 4% higher than the control values. Oppositely, Ca content in patients with TIA and AIS was 9 and 10% lower than the respective control values. The overall tendency was significant in both cases (p < 0.001 and p = 0.007). Serum Cl- level directly correlated with C4 (r = 0.502; p < 0.001), VEGF (r = 0.489; p < 0.001), S100 (r = 0.582; p < 0.001), and NR2Ab (r = 0.589; p < 0.001), whereas Ca was inversely associated with C4 (r = –0.330; p = 0.022) and NR2Ab (r = –0.367; p = 0.010). Despite the absence of significant group difference, serum Na also directly correlated with all studied stroke markers. The results of the study demonstrate a significant alteration of serum Ca and Cl- levels in patients with TIA and AIS and the association between these parameters and brain damage biomarker