This paper is devoted to a theoretical study of the magnetic properties of an ensemble of single-domain interacting magnetic nanoparticles embedded in an immobile polymer matrix. This model is typical for the description of magnetically active polymer ferrocomposites widely used in industrial and biomedical applications. A ferrocomposite is assumed to be produced by carrier medium solidification in a ferrofluid in an external magnetic field hp at a polymerization temperature Tp; after carrier fluid solidification, the nanoparticles retain the spatial distribution and orientation of their easy magnetization axes that they had before carrier medium solidification. The contribution of interparticle dipole–dipole interactions to the static magnetization of a ferrocomposite as a function of the magnetic field strength h and polymerization field hp has been studied separately. The effects of the polymerization temperature and the size of magnetic nanoparticles on the magnetic properties of a ferrocomposite have been analyzed. The analytical expressions for the magnetization and initial magnetic susceptibility presented in the paper make it possible to predict the magnetic properties of a ferrocomposite as a function of its intrinsic characteristics and synthesis conditions, which is a theoretical basis for the production of ferrocomposites with a predetermined magnetic response in a given magnetic field. © 2023, Pleiades Publishing, Inc.