Preparation of n-alkyl group-substituted derivatives of poly(m-aniline) that we have proposed as a possible organic ferromagnetic polymer has been attempted. We started from the syntheses of the monomers, n-alkyl-substituted m-bromoanilines (R = methyl, ethyl, hexyl, dodecyl, and hexyloxy groups). The approximate solubilities of the methyl, ethyl, and hexyloxy group-substituted polymers in N-methyl-2-pyrrolidone (NMP) were nearly equal to that of poly(m-aniline). On the other hand, hexyl- and dodecyl-substituted polymers have high solubilities in the conventional organic solvents such as acetone, dichloromethane, and so forth. The ferromagnetic spin correlation was observed in the polymer oxidized by NOBF4 in the temperature range above 50 K. The average total spin quantum number was determined to be 1.0 at 2 K. Moreover, in all polyradical samples, a weak antiferromagnetic interaction between spin clusters was observed at very low temperatures probably due to a conformational change in the present poly(m-aniline) derivatives.