Embedded materials prepared from MCM-41 together with BE or TON were synthesized, characterized and tested in the ring opening of decalin in a temperature range of 523-623 K. The characterization results revealed that both microporous and mesoporous phases were present in the catalyst. Ir-modification did not change the phase purity, affecting, however, the acidity due to metal-support interactions. The parameters studied in ring opening of decalin were support structure, presence of Ir and temperature. The detailed analysis of 2D/3D isomers and ring opening products showed that the main ring opening products contained ethyl side chain. The Ir-modified embedded mesoporous catalysts were active and relatively selective in the ring opening of decalin, giving 35% selectivity to the ring opening products at 98% conversion at 573 K and 6 MPa.