diff --git a/internal/helper/validation/valid_notification_variables.go b/internal/helper/validation/valid_notification_variables.go
new file mode 100644
index 00000000..261406f6
--- /dev/null
+++ b/internal/helper/validation/valid_notification_variables.go
@@ -0,0 +1,52 @@
+package validation
+
+import (
+	"context"
+
+	"github.com/hashicorp/terraform-plugin-framework/path"
+	"github.com/hashicorp/terraform-plugin-framework/schema/validator"
+
+	"github.com/honeycombio/terraform-provider-honeycombio/internal/models"
+)
+
+var _ validator.Set = notificationVariablesValidator{}
+
+type notificationVariablesValidator struct {
+	schemes []string
+}
+
+func (v notificationVariablesValidator) Description(_ context.Context) string {
+	return "value must be a valid set of webhook variables"
+}
+
+func (v notificationVariablesValidator) MarkdownDescription(ctx context.Context) string {
+	return v.Description(ctx)
+}
+
+func (v notificationVariablesValidator) ValidateSet(ctx context.Context, request validator.SetRequest, response *validator.SetResponse) {
+	if request.ConfigValue.IsNull() || request.ConfigValue.IsUnknown() {
+		return
+	}
+
+	// variable names cannot be duplicated
+	var variables []models.NotificationVariableModel
+	response.Diagnostics.Append(request.ConfigValue.ElementsAs(ctx, &variables, false)...)
+
+	duplicateMap := make(map[string]bool)
+	for i, v := range variables {
+		name := v.Name.ValueString()
+		if duplicateMap[name] {
+			response.Diagnostics.AddAttributeError(
+				path.Root("variable").AtListIndex(i).AtName("name"),
+				"Conflicting configuration arguments",
+				"cannot have more than one \"variable\" with the same \"name\"",
+			)
+		}
+		duplicateMap[name] = true
+	}
+}
+
+// ValidQuerySpec determines if the provided JSON is a valid Honeycomb Query Specification
+func ValidNotificationVariables() validator.Set {
+	return notificationVariablesValidator{}
+}
diff --git a/internal/provider/notification_recipients.go b/internal/provider/notification_recipients.go
index a74775f0..ae57b3fd 100644
--- a/internal/provider/notification_recipients.go
+++ b/internal/provider/notification_recipients.go
@@ -20,6 +20,8 @@ import (
 	"github.com/hashicorp/terraform-plugin-framework/types"
 	"github.com/hashicorp/terraform-plugin-framework/types/basetypes"
 
+	"github.com/honeycombio/terraform-provider-honeycombio/internal/helper/validation"
+
 	"github.com/honeycombio/terraform-provider-honeycombio/client"
 	"github.com/honeycombio/terraform-provider-honeycombio/internal/helper"
 	"github.com/honeycombio/terraform-provider-honeycombio/internal/helper/modifiers"
@@ -90,6 +92,7 @@ func notificationRecipientSchema(allowedTypes []client.RecipientType) schema.Set
 								Description: "The variables to set with the webhook notification.",
 								Validators: []validator.Set{
 									setvalidator.SizeAtMost(10),
+									validation.ValidNotificationVariables(),
 								},
 								NestedObject: schema.NestedBlockObject{
 									Attributes: map[string]schema.Attribute{