Poly-L-, -D-, and -DL-lysine derivatives having pendant nucleic acid bases were prepared by using a polymer modification reaction. Conformation of the polymers was studied by CD and ORD measurements, and the effects of pH of the system, as well as the solvents on the helicity of the polymers were investigated in detail. Further study about the complex formation between the complementary polymers revealed that the complexes are formed by specific base pairing between pendant adenine and thymine or uracil units of the polymers retaining their helical conformations. The photodimerization between thymine containing poly-lysines was studied next over a wide range of pH, and their conformational change was discussed in relation to their functionalities.