diff --git a/.changelog/15999.txt b/.changelog/15999.txt
new file mode 100644
index 000000000..872cd0617
--- /dev/null
+++ b/.changelog/15999.txt
@@ -0,0 +1,3 @@
+```release-note:bug
+acl: Fixed a bug in token creation which failed to parse expiration TTLs correctly
+```
diff --git a/api/acl.go b/api/acl.go
index b8f32441d..1544d1a3c 100644
--- a/api/acl.go
+++ b/api/acl.go
@@ -545,6 +545,53 @@ type ACLTokenRoleLink struct {
 	Name string
 }
 
+// MarshalJSON implements the json.Marshaler interface and allows
+// ACLToken.ExpirationTTL to be marshaled correctly.
+func (a *ACLToken) MarshalJSON() ([]byte, error) {
+	type Alias ACLToken
+	exported := &struct {
+		ExpirationTTL string
+		*Alias
+	}{
+		ExpirationTTL: a.ExpirationTTL.String(),
+		Alias:         (*Alias)(a),
+	}
+	if a.ExpirationTTL == 0 {
+		exported.ExpirationTTL = ""
+	}
+	return json.Marshal(exported)
+}
+
+// UnmarshalJSON implements the json.Unmarshaler interface and allows
+// ACLToken.ExpirationTTL to be unmarshalled correctly.
+func (a *ACLToken) UnmarshalJSON(data []byte) (err error) {
+	type Alias ACLToken
+	aux := &struct {
+		ExpirationTTL any
+		*Alias
+	}{
+		Alias: (*Alias)(a),
+	}
+
+	if err = json.Unmarshal(data, &aux); err != nil {
+		return err
+	}
+	if aux.ExpirationTTL != nil {
+		switch v := aux.ExpirationTTL.(type) {
+		case string:
+			if v != "" {
+				if a.ExpirationTTL, err = time.ParseDuration(v); err != nil {
+					return err
+				}
+			}
+		case float64:
+			a.ExpirationTTL = time.Duration(v)
+		}
+
+	}
+	return nil
+}
+
 type ACLTokenListStub struct {
 	AccessorID string
 	Name       string
diff --git a/command/agent/acl_endpoint_test.go b/command/agent/acl_endpoint_test.go
index 391751150..cfc200445 100644
--- a/command/agent/acl_endpoint_test.go
+++ b/command/agent/acl_endpoint_test.go
@@ -1,6 +1,7 @@
 package agent
 
 import (
+	"bytes"
 	"fmt"
 	"net/http"
 	"net/http/httptest"
@@ -471,6 +472,48 @@ func TestHTTP_ACLTokenCreate(t *testing.T) {
 	})
 }
 
+func TestHTTP_ACLTokenCreateExpirationTTL(t *testing.T) {
+	ci.Parallel(t)
+	httpACLTest(t, nil, func(s *TestAgent) {
+
+		// Generate an example token which has an expiration TTL in string
+		// format.
+		aclToken := `
+{
+  "Name": "Readonly token",
+  "Type": "client",
+  "Policies": ["readonly"],
+  "ExpirationTTL": "10h",
+  "Global": false
+}`
+
+		req, err := http.NewRequest("PUT", "/v1/acl/token", bytes.NewReader([]byte(aclToken)))
+		must.NoError(t, err)
+
+		respW := httptest.NewRecorder()
+		setToken(req, s.RootToken)
+
+		// Make the request.
+		obj, err := s.Server.ACLTokenSpecificRequest(respW, req)
+		must.NoError(t, err)
+		must.NotNil(t, obj)
+
+		// Ensure the returned token includes expiration.
+		createdTokenResp := obj.(*structs.ACLToken)
+		must.Eq(t, "10h0m0s", createdTokenResp.ExpirationTTL.String())
+		must.False(t, createdTokenResp.CreateTime.IsZero())
+
+		// Check for the index.
+		must.StrNotEqFold(t, "", respW.Result().Header.Get("X-Nomad-Index"))
+
+		// Check token was created and stored properly within state.
+		out, err := s.Agent.server.State().ACLTokenByAccessorID(nil, createdTokenResp.AccessorID)
+		must.NoError(t, err)
+		must.NotNil(t, out)
+		must.Eq(t, createdTokenResp, out)
+	})
+}
+
 func TestHTTP_ACLTokenDelete(t *testing.T) {
 	ci.Parallel(t)
 	httpACLTest(t, nil, func(s *TestAgent) {
diff --git a/nomad/structs/acl.go b/nomad/structs/acl.go
index df184358c..158fa81eb 100644
--- a/nomad/structs/acl.go
+++ b/nomad/structs/acl.go
@@ -345,6 +345,57 @@ func (a *ACLToken) HasRoles(roleIDs []string) bool {
 	return true
 }
 
+// MarshalJSON implements the json.Marshaler interface and allows
+// ACLToken.ExpirationTTL to be marshaled correctly.
+func (a *ACLToken) MarshalJSON() ([]byte, error) {
+	type Alias ACLToken
+	exported := &struct {
+		ExpirationTTL string
+		*Alias
+	}{
+		ExpirationTTL: a.ExpirationTTL.String(),
+		Alias:         (*Alias)(a),
+	}
+	if a.ExpirationTTL == 0 {
+		exported.ExpirationTTL = ""
+	}
+	return json.Marshal(exported)
+}
+
+// UnmarshalJSON implements the json.Unmarshaler interface and allows
+// ACLToken.ExpirationTTL to be unmarshalled correctly.
+func (a *ACLToken) UnmarshalJSON(data []byte) (err error) {
+	type Alias ACLToken
+	aux := &struct {
+		ExpirationTTL interface{}
+		Hash          string
+		*Alias
+	}{
+		Alias: (*Alias)(a),
+	}
+
+	if err = json.Unmarshal(data, &aux); err != nil {
+		return err
+	}
+	if aux.ExpirationTTL != nil {
+		switch v := aux.ExpirationTTL.(type) {
+		case string:
+			if v != "" {
+				if a.ExpirationTTL, err = time.ParseDuration(v); err != nil {
+					return err
+				}
+			}
+		case float64:
+			a.ExpirationTTL = time.Duration(v)
+		}
+
+	}
+	if aux.Hash != "" {
+		a.Hash = []byte(aux.Hash)
+	}
+	return nil
+}
+
 // ACLRole is an abstraction for the ACL system which allows the grouping of
 // ACL policies into a single object. ACL tokens can be created and linked to
 // a role; the token then inherits all the permissions granted by the policies.
diff --git a/website/content/api-docs/acl/tokens.mdx b/website/content/api-docs/acl/tokens.mdx
index 2dc2b4596..6b4d014a0 100644
--- a/website/content/api-docs/acl/tokens.mdx
+++ b/website/content/api-docs/acl/tokens.mdx
@@ -201,7 +201,8 @@ The table below shows this endpoint's support for
 
 - `ExpirationTTL` `(duration: 0s)` - This is a convenience field and if set will
   initialize the `ExpirationTime` field to a value of `CreateTime` +
-  `ExpirationTTL`.
+  `ExpirationTTL`. This value must be between the [`token_min_expiration_ttl`][]
+  and [`token_max_expiration_ttl`][] ACL configuration parameters.
 
 ### Sample Payload
 
@@ -499,3 +500,6 @@ $ curl \
   }
 }
 ```
+
+[`token_min_expiration_ttl`]: /nomad/docs/configuration/acl#token_min_expiration_ttl
+[`token_max_expiration_ttl`]: /nomad/docs/configuration/acl#token_max_expiration_ttl