The magnetic properties of polymers containing tetraphenylporphin-Cu(II) (TPP-Cu(II)) or tetraphenylporphin-Ag(II) (TPP-Ag(II)) in the side chains were studied by the magnetic susceptibility (χM) measurement (4—300 K) and ESR spectroscopy. The values of χM for the polymer containing TPP-Cu(II) were found to obey the Curie–Weiss law, and a magnetic moment showed the occurrence of a weak antiferromagnetic interaction between Cu(II) ions. The values of χM for the polymer containing TPP-Ag(II) did not obey any simple equation such as the Curie–Weiss law or Bleaney–Bowers equation and simulation of temperature dependence of χM showed the presence of strongly interacting sites. This strong interaction may possibly arise from a hyperexchange interaction through C = O groups situated among the Ag(II) ions. An ESR study also supported the presence of this interaction between the side groups in a polymer chain.