The conductivities of polyaniline (PANi) composites doped with the copolymeric acids such as poly(methyl methacrylate-co-p-styrenesulfonic acid) (PMMA-co-SSA), poly(styrene-co-p-styrenesulfonic acid) (PS-co-SSA), and poly(methyl methacrylate-co-2-acrylamido-2-methyl-1-propanesulfonic acid) (PMMA-co-AMPS) were investigated as a function of the acid content in the copolymeric acid dopants. With the fixed ratio of acid to aniline (1/1) in the PANi composites, the conductivities of the copolymeric acid-doped PANis decreased as the acid content in the copolymeric acids decreased. This could be attributed to the nonacidic units in the copolymeric acids which seemed to prevent adjacent acid groups from doping the PANi. Among the three kinds of copolymeric acid dopants, the PMMA-co-SSA series doped the PANi most effectively, and consequently, the PMMA-co-SSA-doped PANi composites showed the highest conductivities. The lack of conductivities of the PMMA-co-AMPS-doped PANi composites seems to be due to the doping ability of the AMPS groups. The higher conductivities of the PMMA-co-SSA-doped PANi composites rather than the PS-co-SSA-doped ones were attributed to the hydrogen bonding formed between the carbonyl groups in MMA and the amine groups in aniline which may hinder the phase separation and induce more homogeneous mixing and efficient doping.