diff --git a/cache-config/t3cutil/getdatacfg.go b/cache-config/t3cutil/getdatacfg.go
index 66ffe58ef3..743d4c03f4 100644
--- a/cache-config/t3cutil/getdatacfg.go
+++ b/cache-config/t3cutil/getdatacfg.go
@@ -894,8 +894,8 @@ func FilterDSS(dsses []tc.DeliveryServiceServer, dsIDs map[int]struct{}, serverI
 // FilterParams filters params and returns only the parameters which match configFile, name, and value.
 // If configFile, name, or value is the empty string, it is not filtered.
 // Returns a slice of parameters.
-func FilterParams(params []tc.Parameter, configFile string, name string, value string, omitName string) []tc.Parameter {
-	filtered := []tc.Parameter{}
+func FilterParams(params []tc.ParameterV5, configFile string, name string, value string, omitName string) []tc.ParameterV5 {
+	filtered := []tc.ParameterV5{}
 	for _, param := range params {
 		if configFile != "" && param.ConfigFile != configFile {
 			continue
diff --git a/lib/varnishcfg/custom_vcl.go b/lib/varnishcfg/custom_vcl.go
new file mode 100644
index 0000000000..c71c1fe455
--- /dev/null
+++ b/lib/varnishcfg/custom_vcl.go
@@ -0,0 +1,39 @@
+package varnishcfg
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import (
+	"strings"
+
+	"github.com/apache/trafficcontrol/v8/cache-config/t3cutil"
+)
+
+func (v VCLBuilder) configureCustomVCL(vclFile *vclFile) {
+	params := t3cutil.FilterParams(v.toData.ServerParams, "default.vcl", "", "", "")
+	for _, param := range params {
+		if param.Name == "import" {
+			vclFile.imports = append(vclFile.imports, param.Value)
+			continue
+		}
+		// TODO: support loading vcl files too with `include`?? i.e. `include "custom.vcl";`
+		lines := strings.Split(param.Value, "\n")
+		vclFile.subroutines[param.Name] = append(vclFile.subroutines[param.Name], lines...)
+	}
+}
diff --git a/lib/varnishcfg/custom_vcl_test.go b/lib/varnishcfg/custom_vcl_test.go
new file mode 100644
index 0000000000..e225a5e717
--- /dev/null
+++ b/lib/varnishcfg/custom_vcl_test.go
@@ -0,0 +1,60 @@
+package varnishcfg
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/apache/trafficcontrol/v8/cache-config/t3cutil"
+	"github.com/apache/trafficcontrol/v8/lib/go-tc"
+)
+
+func TestConfigureCustomVCL(t *testing.T) {
+	vb := NewVCLBuilder(&t3cutil.ConfigData{
+		ServerParams: []tc.ParameterV50{
+			{ConfigFile: "default.vcl", Name: "import", Value: "std"},
+			{ConfigFile: "default.vcl", Name: "vcl_recv", Value: "set req.url = std.querysort(req.url);"},
+			{
+				ConfigFile: "default.vcl",
+				Name:       "vcl_deliver",
+				Value:      "if (req.status >= 400 && req.status <= 500) {\n\tset req.status = 404;\n}",
+			},
+		},
+	})
+
+	vclFile := newVCLFile(defaultVCLVersion)
+	vb.configureCustomVCL(&vclFile)
+
+	expectedVCLFile := newVCLFile(defaultVCLVersion)
+	expectedVCLFile.imports = append(expectedVCLFile.imports, "std")
+	expectedVCLFile.subroutines["vcl_recv"] = []string{
+		"set req.url = std.querysort(req.url);",
+	}
+	expectedVCLFile.subroutines["vcl_deliver"] = []string{
+		"if (req.status >= 400 && req.status <= 500) {",
+		"	set req.status = 404;",
+		"}",
+	}
+
+	if !reflect.DeepEqual(vclFile, expectedVCLFile) {
+		t.Errorf("got %v want %v", vclFile, expectedVCLFile)
+	}
+}
diff --git a/lib/varnishcfg/vclbuilder.go b/lib/varnishcfg/vclbuilder.go
index 91b14b5f6b..68f903dd34 100644
--- a/lib/varnishcfg/vclbuilder.go
+++ b/lib/varnishcfg/vclbuilder.go
@@ -88,5 +88,7 @@ func (vb *VCLBuilder) BuildVCLFile() (string, []string, error) {
 	dirWarnings, err := vb.configureDirectors(&v, parents)
 	warnings = append(warnings, dirWarnings...)
 
+	vb.configureCustomVCL(&v)
+
 	return fmt.Sprint(v), warnings, err
 }