The correlation between the tensile strength and corrosion behavior of Zr-1.0wt%Nb alloy heat treated at $480^{circ}C$ for up to 32 hours was evaluated. The tensile strength at $400^{circ}C$ was continuously reduced with an increasing heat treatment time, mainly due to a grain growth and a decreased area fraction of the precipitates. However, the corrosion resistance in an aqueous ammonia solution at $360^{circ}C$ was enhanced, mainly due to the formation of $eta$-Nb precipitates. It is thus concluded that a longer heat treatment time provides a better corrosion resistance while degrading the tensile strength.