diff --git a/src/core/thread/mesh_forwarder_ftd.cpp b/src/core/thread/mesh_forwarder_ftd.cpp
index 12accafa4..4001bbeb5 100644
--- a/src/core/thread/mesh_forwarder_ftd.cpp
+++ b/src/core/thread/mesh_forwarder_ftd.cpp
@@ -511,7 +511,7 @@ Error MeshForwarder::UpdateIp6RouteFtd(const Ip6::Header &aIp6Header, Message &a
     else if (mle.IsRoutingLocator(aIp6Header.GetDestination()))
     {
         uint16_t rloc16 = aIp6Header.GetDestination().GetIid().GetLocator();
-        VerifyOrExit(mle.IsRouterIdValid(Mle::RouterIdFromRloc16(rloc16)), error = kErrorDrop);
+        VerifyOrExit(Mle::IsRouterIdValid(Mle::RouterIdFromRloc16(rloc16)), error = kErrorDrop);
         mMeshDest = rloc16;
     }
     else if (mle.IsAnycastLocator(aIp6Header.GetDestination()))
diff --git a/src/core/thread/mle_router.hpp b/src/core/thread/mle_router.hpp
index fd876044a..048d901d9 100644
--- a/src/core/thread/mle_router.hpp
+++ b/src/core/thread/mle_router.hpp
@@ -421,17 +421,6 @@ class MleRouter : public Mle
      */
     void ResolveRoutingLoops(uint16_t aSourceMac, uint16_t aDestRloc16);
 
-    /**
-     * Checks if a given Router ID has correct value.
-     *
-     * @param[in]  aRouterId  The Router ID value.
-     *
-     * @retval TRUE   If @p aRouterId is in correct range [0..62].
-     * @retval FALSE  If @p aRouterId is not a valid Router ID.
-     *
-     */
-    static bool IsRouterIdValid(uint8_t aRouterId) { return aRouterId <= kMaxRouterId; }
-
     /**
      * Fills an ConnectivityTlv.
      *
@@ -799,8 +788,6 @@ class MleRouter : public Mle
     Error RemoveNeighbor(Neighbor &) { return BecomeDetached(); }
     void  RemoveRouterLink(Router &) { IgnoreError(BecomeDetached()); }
 
-    static bool IsRouterIdValid(uint8_t aRouterId) { return aRouterId <= kMaxRouterId; }
-
     Error SendChildUpdateRequest(void) { return Mle::SendChildUpdateRequest(); }
 
     Error CheckReachability(uint16_t aMeshDest, const Ip6::Header &aIp6Header)
diff --git a/src/core/thread/mle_types.hpp b/src/core/thread/mle_types.hpp
index ae4dfdfa3..ab2a7b02d 100644
--- a/src/core/thread/mle_types.hpp
+++ b/src/core/thread/mle_types.hpp
@@ -616,6 +616,17 @@ inline uint16_t ChildIdFromRloc16(uint16_t aRloc16) { return aRloc16 & kMaxChild
  */
 inline uint8_t RouterIdFromRloc16(uint16_t aRloc16) { return aRloc16 >> kRouterIdOffset; }
 
+/**
+ * Indicates whether or not a given Router ID is valid.
+ *
+ * @param[in]  aRouterId  The Router ID value to check.
+ *
+ * @retval TRUE   If @p aRouterId is in correct range [0..62].
+ * @retval FALSE  If @p aRouterId is not a valid Router ID.
+ *
+ */
+inline bool IsRouterIdValid(uint8_t aRouterId) { return aRouterId <= kMaxRouterId; }
+
 /**
  * Returns whether the two RLOC16 have the same Router ID.
  *