diff --git a/src/core/meshcop/commissioner.cpp b/src/core/meshcop/commissioner.cpp
index 78bf2adb6..c6e522409 100644
--- a/src/core/meshcop/commissioner.cpp
+++ b/src/core/meshcop/commissioner.cpp
@@ -1221,22 +1221,17 @@ exit:
 
 const char *Commissioner::StateToString(State aState)
 {
-    const char *str = "Unknown";
+    static const char *const kStateStrings[] = {
+        "disabled", // (0) kStateDisabled
+        "petition", // (1) kStatePetition
+        "active",   // (2) kStateActive
+    };
 
-    switch (aState)
-    {
-    case kStateDisabled:
-        str = "disabled";
-        break;
-    case kStatePetition:
-        str = "petition";
-        break;
-    case kStateActive:
-        str = "active";
-        break;
-    }
+    static_assert(kStateDisabled == 0, "kStateDisabled value is incorrect");
+    static_assert(kStatePetition == 1, "kStatePetition value is incorrect");
+    static_assert(kStateActive == 2, "kStateActive value is incorrect");
 
-    return str;
+    return kStateStrings[aState];
 }
 
 void Commissioner::LogJoinerEntry(const char *aAction, const Joiner &aJoiner) const
diff --git a/src/core/meshcop/joiner.cpp b/src/core/meshcop/joiner.cpp
index 6ff590324..a62bb288f 100644
--- a/src/core/meshcop/joiner.cpp
+++ b/src/core/meshcop/joiner.cpp
@@ -653,31 +653,23 @@ void Joiner::HandleTimer(void)
 
 const char *Joiner::StateToString(State aState)
 {
-    const char *str = "Unknown";
+    static const char *const kStateStrings[] = {
+        "Idle",       // (0) kStateIdle
+        "Discover",   // (1) kStateDiscover
+        "Connecting", // (2) kStateConnect
+        "Connected",  // (3) kStateConnected
+        "Entrust",    // (4) kStateEntrust
+        "Joined",     // (5) kStateJoined
+    };
 
-    switch (aState)
-    {
-    case kStateIdle:
-        str = "Idle";
-        break;
-    case kStateDiscover:
-        str = "Discover";
-        break;
-    case kStateConnect:
-        str = "Connecting";
-        break;
-    case kStateConnected:
-        str = "Connected";
-        break;
-    case kStateEntrust:
-        str = "Entrust";
-        break;
-    case kStateJoined:
-        str = "Joined";
-        break;
-    }
+    static_assert(kStateIdle == 0, "kStateIdle value is incorrect");
+    static_assert(kStateDiscover == 1, "kStateDiscover value is incorrect");
+    static_assert(kStateConnect == 2, "kStateConnect value is incorrect");
+    static_assert(kStateConnected == 3, "kStateConnected value is incorrect");
+    static_assert(kStateEntrust == 4, "kStateEntrust value is incorrect");
+    static_assert(kStateJoined == 5, "kStateJoined value is incorrect");
 
-    return str;
+    return kStateStrings[aState];
 }
 
 #if OPENTHREAD_CONFIG_REFERENCE_DEVICE_ENABLE