Interaction of metal(II) thiocyanato complexes and 1,10-phenanthroline (phen) with nonionic micelles of poly(ethylene oxide) type surfactants with varying its chain length has been investigated by potentiometry, titration spectrophotometry and calorimetry at 298K. In the case of phen and Cu(NCS)₂, only nonionic species are distributed into a micellar phase, while Co(NCS)₄^2- forms uniquely in a micellar phase. The thermodynamic parameters, i.e., Gibbs energies, enthalpies and entropies of transfer from an aqueous to micellar phase and/or of the complex formation in micellar phase significantly depend on the chain length of poly(ethylene oxide). This suggests the intramicellar heterogeneous structure consists of poly(ethylene oxide) region and octylphenyl one. The intrinsic thermodynamic parameters of transfer and/or the complex formation in each region have been determined.