On the basis of the data of ESR and magnetic susceptibility of Bi₂BaNb_2–2xMn_2xO_9–δ solid solutions with perovskite-like structure ferro- and aniferromagnetic bonded dimers, trimers, and tetramers of Mn(II), Mn(III), and Mn(IV) atoms in various valence states were found. The distribution of aggregates and exchange parameters in the clusters were calculated as a function of fraction x of manganese atoms in the solid solutions. In the ESR spectra of diluted solid solutions there are absorption bands with g-factors ~4.3 and 2.1 assigned to Mn(II) and Mn(IV) atoms.