Palladium‐1,10‐phenanthroline‐catalyzed chelation‐assisted direct C‐H bond arylation of thienylthioamide was developed. The base used critically affected the reactivity, and β‐selective (3‐selective) reaction took place with K2CO3, and both α and β‐positions were arylated to give 3,5‐diarylated product when Cs2CO3 was used. The chelation‐assisted palladation to give palladacycles was confirmed by the stoichiometric reactions of thienylthioamide and the catalyst precursor.