An n-butanol-based nanofluid containing nanowire-shaped beta-FeOOH was synthesized by a solvothermal method. The nanofluid was stable for 7 days without any precipitation with 3.0 mM SDBS as stabilizer. Uniform beta-FeOOH nanowires with high aspect ratios were fabricated. The heat capacities of the obtained beta-FeOOH sample, the base fluid, and the nanofluid were determined by an adiabatic calorimeter. Smoothed heat capacities and thermodynamic functions of the obtained samples, such as H(T/K) - H(298.15 K) and S(T/K) - S(298.15 K), were calculated based on the fitted polynomials and the relationships of the thermodynamic functions. These results are very useful to apply to the as-produced nanowire-shaped beta-FeOOH and the nanofluid in engineering fields.