We have synthesized a red biarsenical fluorescent probe, AsCy3, with good photostability, low pH sensitivity, high absorbance, and good quantum yield. It is directed specifically to a small tetracysteine peptide binding motif, Cy3TAG (CysCysLysAlaGluAlaAlaCysCys), in the presence of other tetracysteine tags. This new probe provides a FRET partner to biarsenical dye FlAsH, making this discovery an important step toward a whole toolkit of colored probes directed to different small peptide motifs.