The aggregation-induced phosphorescence emission (AIPE) phenomenon (emergence or increase in phosphorescence intensity as a result of aggregation of phosphorescent emitters) is regarded nowadays as an effective tool for improving brightness and tuning photophysical properties of phosphors. The intrinsic drawback of the aggregates featuring AIPE—their instability in aqueous dispersions, which hampers their utility in biomedical applications—can be overcome by their stabilization inside block copolymer micelles. Herein, we investigate the effects of both ligand and micellar core chemistries on the emergence of AIPE by using a series of the [Pt(C^N*N′^C′)] complexes embedded into three block copolymers with different micellar cores. It has been shown that the only micelles that supported AIPE revealed for the corresponding complexes in solid state are those with poly(ε-caprolactone) cores. The latter observation can be explained by the ability of poly(ε-caprolactone) to demonstrate non-negligible swelling in water, the content of which in the micellar core formed by this polymer seems to be high enough to induce the aggregation of the complexes and the concomitant AIPE effect.