Efficient heat dissipation through thermal interface materials is a critical challenge in the advancement of modern microelectronic devices. Traditional polymer composites, even when loaded with highly thermally conductive fillers, often exhibit limited thermal conductivity due to the absence of effective heat transfer pathways. In this study, vertically aligned and interconnected boron nitride (BN) networks are employed as fillers, fabricated using a controlled three-step process: the formation of cellulose/BN hydrogel, oriented freeze casting, and vacuum impregnation. The resulting composite, with an ultralow BN loading of 0.5 vol %, achieves a remarkably high thermal conductivity of 2.86 W m⁻¹ K. Additionally, the composite demonstrates a significantly reduced coefficient of thermal expansion. This approach offers valuable insights into the development of high-performance composites for potential applications in advanced electronic packaging.