Based on density functional theory, we recently suggested that metastable α-WB2 is a promising candidate combining very high hardness with high toughness. These calculations further suggested that the addition of Tantalum supports the crystallization of α-structured W1−xTaxB2−z, with only minor reduction in toughness. Thus, various Ta containing WB2-based coatings have been synthesized using physical vapor deposition. With increasing Ta content, the hardness increases from ~41 GPa (WB2) to ~45 GPa (W0.74Ta0.26B2). In situ micromechanical cantilever bending tests exhibit fracture toughness KIC values of 3.7 to 3.0 MPa√m for increasing Ta content (single-phased up to 26 at.% Ta).