This study presents a direct ink writing (DIW) method for 3D printing of nanocellulose aerogels, which exhibit tunable anisotropic mechanical and thermal properties. By incorporating fibers of different lengths into the hydrogel inks, the aerogels show enhanced mechanical strength and thermal resistance, with higher longitudinal thermal conductivity (65 mW m⁻¹ K⁻¹) compared to transverse (24 mW m⁻¹ K⁻¹). The rehydration of printed aerogels for biomedical applications preserves their high surface area while improving mechanical properties in the transverse direction. The aerogels demonstrate excellent cellular viability (>90% for NIH/3T3 fibroblasts) and exhibit robust antibacterial activity through in situ-grown silver nanoparticles. The study highlights the potential of DIW printing for creating complex, customized cellulose aerogels with tailored properties for various applications, particularly in thermal insulation and biomedical fields.This study presents a direct ink writing (DIW) method for 3D printing of nanocellulose aerogels, which exhibit tunable anisotropic mechanical and thermal properties. By incorporating fibers of different lengths into the hydrogel inks, the aerogels show enhanced mechanical strength and thermal resistance, with higher longitudinal thermal conductivity (65 mW m⁻¹ K⁻¹) compared to transverse (24 mW m⁻¹ K⁻¹). The rehydration of printed aerogels for biomedical applications preserves their high surface area while improving mechanical properties in the transverse direction. The aerogels demonstrate excellent cellular viability (>90% for NIH/3T3 fibroblasts) and exhibit robust antibacterial activity through in situ-grown silver nanoparticles. The study highlights the potential of DIW printing for creating complex, customized cellulose aerogels with tailored properties for various applications, particularly in thermal insulation and biomedical fields.