Firiza basaltic complex (FBC) is the final volcanic phase (8.1–7.0 Ma) of the Gutâi Volcanic Zone (GVZ) from the Neogene–Quaternary volcanic chain of the Eastern Carpathians (Romania). Nine small intrusions of the FBC crosscut older volcanic products (11.3–9.0 Ma) and consist of microporphyritic–aphanitic basalts. The volcanic rocks from GVZ, and FBC show typical arc-related geochemical features (calc-alkaline). Based on the chemical composition of the studied clinopyroxenes, the cores of the clinopyroxene phenocrysts and glomerocrysts are the most primitive (Mg#: 79–91) and alongside the olivine were the first crystallized phases. A deep magma source (22–30 km depth) in the lower crust near the MOHO (33–35 km depth in GVZ) is indicated by the crystallization pressures (~5.5–8.5 kbar) of the clinopyroxene cores. By studying the clinopyroxene cores with Fourier Transform Infrared spectrometry information for their structural hydroxyl content, ‘water’ content of their parental melt, and ‘water’ content of the mantle source region can be obtained. The structural hydroxyl content of the clinopyroxenes is relatively high (105–515 wt. ppm). The corresponding equilibrium melt ‘water’ contents (1.85–3.91 wt. %) and upper mantle source ‘water’ contents (2200–5200 wt. ppm) overlap with values reported from island arc basalts (IAB) and are higher than those from the alkali basalts from the Bakony–Balaton Highland Volcanic Field (BBHVF) (1.2–2.1 wt. % and 400–520 wt. ppm). The reason behind this is the different geodynamic positions of the two areas, the GVZ is in the close vicinity of a recent subduction whereas the BBHVF is not. This is the first work dealing with the ‘water’ content of calc-alkaline melts from the region.