A new chemical method is developed for the preparation of a unique one-dimensional (1D) Sn(IV) hydroxide nanofluid. The 1D-Sn(IV) hydroxide nanowires of ca. 600 nm in length and ca. 25 nm in width yield transparent glass type flakes when the nanofluid is dried in air. The stability of the system, keeping it safe from sedimentation even after a year, is believed to rely on its high zeta-potential of ca. 55 mV (± 2.5 mV). We extensively investigate the thermal conductivity and viscosity of the system in order to evaluate its nanofluidic merits, resulting in thermal conductivity exceeding 1 W m−1 K−1. The nanofluid is further investigated for nonlinear optics (NLO) applications, revealing a reversible switching from positive Z-scan (convex lens) to negative Z-scan (concave lens) of the nonlinear phase when the laser power is tuned from 500 to 1000 μW.