Let $A/K$ be an abelian variety over a number field, let $\mathfrak{p}$ be a finite prime of $K$, and let $p$ be the residue characteristic of $\mathfrak{p}$. For each rational prime $l \ne p$, let $V_lA := T_lA \otimes_{\mathbb{Z}_l} \mathbb{Q}_l$ be the rational $l$-adic Tate module representation of $G_K := \operatorname{Gal}(\overline{K}/K)$. Then $A$ has good reduction at $\mathfrak{p}$ if and only if, for one rational prime $l \ne p$, the representation $V_lA$ is unramified at $\mathfrak{p}$. In that case, $V_lA$ is unramified at $\mathfrak{p}$ for every rational prime $l \ne p$.