Generally, tetrahedrally coordinated Ag-based chalcogenides have wider band gaps than their Cu-based counterparts. Recent studies have suggested Cu3SbS4 as the absorber in low-cost and low-toxicity photovoltaic (PV), however its band gap is ∼0.5 eV smaller than the ideal value of ∼1.3 eV. In this work, we investigate Ag3SbS4 by first-principles means, since one can anticipate improved optical properties for this compound. The results indeed demonstrate that enargite Ag3SbS4 is a direct-gap semiconductor with a band gap of 1.38 eV, thus optimal for single-junction solar cells. Furthermore, its carrier effective masses, optical coefficients and spectroscopic limited maximum efficiency are comparable to well-established PV compounds. The compound exhibits also thermodynamical and dynamical stability. Hence, based on the present theoretical study we predict that Ag3SbS4 could be a candidate for absorber in high-efficient thin-film PVs.