A new family of poly(phenylene-pyridyl) dendrimers (up to the fourth generation) with different periphery was synthesized via a divergent route by using a cascade of Diels-Alder cycloadditions. Tetra(4-ethynylphen-1-yl)methane served as a core. A new A(2)B cyclopentadienone building block, namely, pyridine-containing cyclopentadienone with protected dienophile functions was prepared. By varying the building blocks at the last step of dendrimer construction, one could design molecules possessing either a phenyl- or a pyridyl-decorated outershell. The products were characterized by NMR spectroscopy, MALDI-TOF mass spectrometry, elemental analysis, atomic force microscopy, thermogravimetric analysis, DSC, and dynamic light scattering methods. These stiff polyphenylene dendrimers with pyridine embeds were then used as a matrix for encapsulation of Pd nanoparticles. The fourth-generation poly(phenylene-pyridyl) dendrimer with a phenyl-decorated periphery and pyridine-containing interior was found to serve as a powerful template for metal nanoparticle formation, resulting in excellent nanoparticle stability (no precipitation was observed for more than 6 months).