diff --git a/config/module/test-fixtures/validate-child-bad/child/main.tf b/config/module/test-fixtures/validate-child-bad/child/main.tf
new file mode 100644
index 000000000..93b365403
--- /dev/null
+++ b/config/module/test-fixtures/validate-child-bad/child/main.tf
@@ -0,0 +1,3 @@
+# Duplicate resources
+resource "aws_instance" "foo" {}
+resource "aws_instance" "foo" {}
diff --git a/config/module/test-fixtures/validate-child-bad/main.tf b/config/module/test-fixtures/validate-child-bad/main.tf
new file mode 100644
index 000000000..813f7ef8e
--- /dev/null
+++ b/config/module/test-fixtures/validate-child-bad/main.tf
@@ -0,0 +1,3 @@
+module "foo" {
+    source = "./child"
+}
diff --git a/config/module/test-fixtures/validate-child-good/child/main.tf b/config/module/test-fixtures/validate-child-good/child/main.tf
new file mode 100644
index 000000000..dd0d95b59
--- /dev/null
+++ b/config/module/test-fixtures/validate-child-good/child/main.tf
@@ -0,0 +1 @@
+# Good
diff --git a/config/module/test-fixtures/validate-child-good/main.tf b/config/module/test-fixtures/validate-child-good/main.tf
new file mode 100644
index 000000000..0f6991c53
--- /dev/null
+++ b/config/module/test-fixtures/validate-child-good/main.tf
@@ -0,0 +1,3 @@
+module "child" {
+    source = "./child"
+}
diff --git a/config/module/test-fixtures/validate-root-bad/main.tf b/config/module/test-fixtures/validate-root-bad/main.tf
new file mode 100644
index 000000000..93b365403
--- /dev/null
+++ b/config/module/test-fixtures/validate-root-bad/main.tf
@@ -0,0 +1,3 @@
+# Duplicate resources
+resource "aws_instance" "foo" {}
+resource "aws_instance" "foo" {}
diff --git a/config/module/tree.go b/config/module/tree.go
index d08b047bd..2ac3f8b18 100644
--- a/config/module/tree.go
+++ b/config/module/tree.go
@@ -67,6 +67,13 @@ func (t *Tree) Flatten() (*config.Config, error) {
 	return nil, nil
 }
 
+// Loaded says whether or not this tree has been loaded or not yet.
+func (t *Tree) Loaded() bool {
+	t.lock.RLock()
+	defer t.lock.RUnlock()
+	return t.children != nil
+}
+
 // Modules returns the list of modules that this tree imports.
 //
 // This is only the imports of _this_ level of the tree. To retrieve the
@@ -191,6 +198,58 @@ func (t *Tree) String() string {
 //
 // This will call the respective config.Config.Validate() functions as well
 // as verifying things such as parameters/outputs between the various modules.
+//
+// Load must be called prior to calling Validate or an error will be returned.
 func (t *Tree) Validate() error {
+	if !t.Loaded() {
+		return fmt.Errorf("tree must be loaded before calling Validate")
+	}
+
+	// Validate our configuration first.
+	if err := t.config.Validate(); err != nil {
+		return &ValidateError{
+			Name: []string{t.Name()},
+			Err:  err,
+		}
+	}
+
+	// Validate all our children
+	for _, c := range t.Children() {
+		err := c.Validate()
+		if err == nil {
+			continue
+		}
+
+		verr, ok := err.(*ValidateError)
+		if !ok {
+			// Unknown error, just return...
+			return err
+		}
+
+		// Append ourselves to the error and then return
+		verr.Name = append(verr.Name, t.Name())
+		return verr
+	}
+
 	return nil
 }
+
+// ValidateError is an error returned by Tree.Validate if an error occurs
+// with validation.
+type ValidateError struct {
+	Name []string
+	Err  error
+}
+
+func (e *ValidateError) Error() string {
+	// Build up the name
+	var buf bytes.Buffer
+	for _, n := range e.Name {
+		buf.WriteString(n)
+		buf.WriteString(".")
+	}
+	buf.Truncate(buf.Len()-1)
+
+	// Format the value
+	return fmt.Sprintf("module %s: %s", buf.String(), e.Err)
+}
diff --git a/config/module/tree_test.go b/config/module/tree_test.go
index fe9e09604..8795e16b9 100644
--- a/config/module/tree_test.go
+++ b/config/module/tree_test.go
@@ -6,20 +6,32 @@ import (
 	"testing"
 )
 
-func TestTree_Load(t *testing.T) {
+func TestTreeLoad(t *testing.T) {
 	storage := testStorage(t)
 	tree := NewTree(testConfig(t, "basic"))
 
+	if tree.Loaded() {
+		t.Fatal("should not be loaded")
+	}
+
 	// This should error because we haven't gotten things yet
 	if err := tree.Load(storage, GetModeNone); err == nil {
 		t.Fatal("should error")
 	}
 
+	if tree.Loaded() {
+		t.Fatal("should not be loaded")
+	}
+
 	// This should get things
 	if err := tree.Load(storage, GetModeGet); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
+	if !tree.Loaded() {
+		t.Fatal("should be loaded")
+	}
+
 	// This should no longer error
 	if err := tree.Load(storage, GetModeNone); err != nil {
 		t.Fatalf("err: %s", err)
@@ -32,7 +44,7 @@ func TestTree_Load(t *testing.T) {
 	}
 }
 
-func TestTree_Modules(t *testing.T) {
+func TestTreeModules(t *testing.T) {
 	tree := NewTree(testConfig(t, "basic"))
 	actual := tree.Modules()
 
@@ -45,7 +57,7 @@ func TestTree_Modules(t *testing.T) {
 	}
 }
 
-func TestTree_Name(t *testing.T) {
+func TestTreeName(t *testing.T) {
 	tree := NewTree(testConfig(t, "basic"))
 	actual := tree.Name()
 
@@ -54,6 +66,50 @@ func TestTree_Name(t *testing.T) {
 	}
 }
 
+func TestTreeValidate_badChild(t *testing.T) {
+	tree := NewTree(testConfig(t, "validate-child-bad"))
+
+	if err := tree.Load(testStorage(t), GetModeGet); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if err := tree.Validate(); err == nil {
+		t.Fatal("should error")
+	}
+}
+
+func TestTreeValidate_badRoot(t *testing.T) {
+	tree := NewTree(testConfig(t, "validate-root-bad"))
+
+	if err := tree.Load(testStorage(t), GetModeGet); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if err := tree.Validate(); err == nil {
+		t.Fatal("should error")
+	}
+}
+
+func TestTreeValidate_good(t *testing.T) {
+	tree := NewTree(testConfig(t, "validate-child-good"))
+
+	if err := tree.Load(testStorage(t), GetModeGet); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if err := tree.Validate(); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+}
+
+func TestTreeValidate_notLoaded(t *testing.T) {
+	tree := NewTree(testConfig(t, "basic"))
+
+	if err := tree.Validate(); err == nil {
+		t.Fatal("should error")
+	}
+}
+
 const treeLoadStr = `
 <root>
   foo