We report two novel azaisoindigo and benzothiadiazole-containing ternary copolymers PAZDTBT and PAZDTBTF. The thermal, optical and electrochemical properties, conjugated backbone planarity, film morphology and molecular packing mode, as well as charge transport characteristics of two copolymers, were studied systematically through either experimental evaluations or theoretical modellings. The copolymer PAZDTBTF containing fluorine atoms on benzothiadiazole units owns an energy level of the lowest unoccupied molecular orbital (LUMO) (−3.56 eV) similar to that of non-fluorinated copolymer PAZDTBT (−3.53 eV). Both ternary copolymers PAZDTBT and PAZDTBTF exhibited ambipolar charge carrier transport characteristics. When compared with the averaged hole/electron mobilities of 0.377 and 0.092 cm2 V−1 s−1 for PAZDTBT, the polymer PAZDTBTF has an enhanced electron mobility of 0.126 cm2 V−1 s−1, though its hole mobility of 0.358 cm2 V−1 s−1 was a little bit lower than that of PAZDTBT. Our work demonstrates the great potentials of ternary π-conjugated system with two different acceptor units in fine-tuning the optoelectronic properties of polymer semiconductors.