Vinyl ether-modified poly(hydrogen silsesquioxanes) or PHSQ were prepared via a platinum-catalyzed hydrosilylation reaction of PHSQ with an alkyl vinyl ether (VE) in toluene. The product formed in a near quantitative yield and its composition was characterized by multinuclear magnetic resonance spectroscopy. Multi-detector size exclusion chromatography revealed that relative to the PHSQ starting material, the PHSQ–VEs increased in molecular weight and radius of gyration, and the relationship between intrinsic viscosity and molecular weight suggested a branched structure. Thermal analyses indicated a cure onset around 100 °C; an onset of thermal decomposition at ca. 230 °C; and mass loss completed by 550 °C. Evolved gas analysis from thermogravimetric experiments revealed the initial elimination of the ethylene linkage, followed by cleavage of the carbon–carbon bonds. The materials prepared by pyrolysis at 425 °C were porous. Nitrogen porosimetry measured an increase in microporosity—from 0.187 to 0.295 cm³ g⁻¹ (<5 nm)—when the VE content was increased from 10 to 50 wt%. The PHSQ–VEs were spin-coated onto silicon wafers and cured either at 400, 425, or 450 °C. The dielectric constant of the spin-coated films ranged from 2.3 to 3.0, and the modulus was between 2.2 and 12.9 GPa depending on material composition.