diff --git a/apps/rush-lib/src/api/CommandLineJson.ts b/apps/rush-lib/src/api/CommandLineJson.ts
index 6946dda647a..c189964a007 100644
--- a/apps/rush-lib/src/api/CommandLineJson.ts
+++ b/apps/rush-lib/src/api/CommandLineJson.ts
@@ -38,7 +38,7 @@ export type CommandJson = IBulkCommandJson | IGlobalCommandJson;
  * "baseParameter" from command-line.schema.json
  */
 export interface IBaseParameterJson {
-  parameterKind: 'flag' | 'choice';
+  parameterKind: 'flag' | 'choice' | 'string';
   longName: string;
   shortName?: string;
   description: string;
@@ -69,7 +69,12 @@ export interface IChoiceParameterJson extends IBaseParameterJson {
   defaultValue?: string;
 }
 
-export type ParameterJson = IFlagParameterJson | IChoiceParameterJson;
+export interface IStringParameterJson extends IBaseParameterJson {
+  parameterKind: 'string';
+  argumentName: string;
+}
+
+export type ParameterJson = IFlagParameterJson | IChoiceParameterJson | IStringParameterJson;
 
 /**
  * Interfaces for the file format described by command-line.schema.json
diff --git a/apps/rush-lib/src/cli/scriptActions/BaseScriptAction.ts b/apps/rush-lib/src/cli/scriptActions/BaseScriptAction.ts
index ba5df017d00..f8fb5a2a5e6 100644
--- a/apps/rush-lib/src/cli/scriptActions/BaseScriptAction.ts
+++ b/apps/rush-lib/src/cli/scriptActions/BaseScriptAction.ts
@@ -68,6 +68,14 @@ export abstract class BaseScriptAction extends BaseRushAction {
               defaultValue: parameter.defaultValue
             });
             break;
+          case 'string':
+            customParameter = this.defineStringParameter({
+              parameterLongName: parameter.longName,
+              parameterShortName: parameter.shortName,
+              description: parameter.description,
+              argumentName: parameter.argumentName
+            });
+            break;
           default:
             throw new Error(`${RushConstants.commandLineFilename} defines a parameter "${parameter!.longName}"`
               + ` using an unsupported parameter kind "${parameter!.parameterKind}"`);
diff --git a/apps/rush-lib/src/schemas/command-line.schema.json b/apps/rush-lib/src/schemas/command-line.schema.json
index a173a87ef44..30375dae20f 100644
--- a/apps/rush-lib/src/schemas/command-line.schema.json
+++ b/apps/rush-lib/src/schemas/command-line.schema.json
@@ -135,9 +135,9 @@
       "properties": {
         "parameterKind": {
           "title": "Parameter Kind",
-          "description": "Indicates the kind of syntax for this command-line parameter: \"flag\" or \"choice\"",
+          "description": "Indicates the kind of syntax for this command-line parameter: \"flag\" or \"choice\" or \"string\"",
           "type": "string",
-          "enum": [ "flag", "choice" ]
+          "enum": [ "flag", "choice", "string" ]
         },
         "longName": {
           "title": "Long Name",
@@ -195,6 +195,41 @@
         }
       ]
     },
+    "stringParameter": {
+      "title": "String Parameter",
+      "description": "A custom command-line parameter whose value is intepreted as a string",
+      "type": "object",
+      "allOf": [
+        { "$ref": "#/definitions/baseParameter" },
+        {
+          "type": "object",
+          "additionalProperties": true,
+          "required": ["argumentName"],
+          "properties": {
+            "parameterKind": {
+              "enum": [ "string" ]
+            },
+            "argumentName": {
+              "title": "Argument Name",
+              "description": "The name of the argument for this parameter.",
+              "type": "string"
+            }
+          }
+        },
+        {
+          "type": "object",
+          "additionalProperties": false,
+          "properties": {
+            "parameterKind": { "$ref": "#/definitions/anything" },
+            "longName": { "$ref": "#/definitions/anything" },
+            "shortName": { "$ref": "#/definitions/anything" },
+            "description": { "$ref": "#/definitions/anything" },
+            "associatedCommands": { "$ref": "#/definitions/anything" },
+            "argumentName": { "$ref": "#/definitions/anything" }
+          }
+        }
+      ]
+    },
     "choiceParameter": {
       "title": "Choice Parameter",
       "description": "A custom command-line parameter whose argument must be chosen from a list of allowable alternatives",
@@ -287,7 +322,8 @@
         "type": "object",
         "oneOf": [
           { "$ref": "#/definitions/flagParameter" },
-          { "$ref": "#/definitions/choiceParameter" }
+          { "$ref": "#/definitions/choiceParameter" },
+          { "$ref": "#/definitions/stringParameter" }
         ]
       }
     }
diff --git a/common/changes/@microsoft/rush/kinhln-string-param_2019-03-28-00-55.json b/common/changes/@microsoft/rush/kinhln-string-param_2019-03-28-00-55.json
new file mode 100644
index 00000000000..a709ea5dd1f
--- /dev/null
+++ b/common/changes/@microsoft/rush/kinhln-string-param_2019-03-28-00-55.json
@@ -0,0 +1,11 @@
+{
+  "changes": [
+    {
+      "comment": "Add support for string parameter for custom commands.",
+      "packageName": "@microsoft/rush",
+      "type": "none"
+    }
+  ],
+  "packageName": "@microsoft/rush",
+  "email": "kinhln@microsoft.com"
+}
\ No newline at end of file