diff --git a/mask-parser/src/maskfile.rs b/mask-parser/src/maskfile.rs
index c5f0f28..cf35293 100644
--- a/mask-parser/src/maskfile.rs
+++ b/mask-parser/src/maskfile.rs
@@ -22,6 +22,7 @@ pub struct Command {
     pub script: Option<Script>,
     pub subcommands: Vec<Command>,
     pub required_args: Vec<RequiredArg>,
+    pub optional_args: Vec<OptionalArg>,
     pub named_flags: Vec<NamedFlag>,
 }
 
@@ -34,6 +35,7 @@ impl Command {
             script: Some(Script::new()),
             subcommands: vec![],
             required_args: vec![],
+            optional_args: vec![],
             named_flags: vec![],
         }
     }
@@ -99,6 +101,23 @@ impl RequiredArg {
     }
 }
 
+#[derive(Debug, Serialize, Clone)]
+pub struct OptionalArg {
+    pub name: String,
+    /// Used within mask. TODO: store in a different place within mask instead of here.
+    #[serde(skip)]
+    pub val: String,
+}
+
+impl OptionalArg {
+    pub fn new(name: String) -> Self {
+        Self {
+            name,
+            val: "".to_string(),
+        }
+    }
+}
+
 #[derive(Debug, Serialize, Clone)]
 pub struct NamedFlag {
     pub name: String,
diff --git a/mask-parser/src/parser.rs b/mask-parser/src/parser.rs
index 9971f2d..dffb50a 100644
--- a/mask-parser/src/parser.rs
+++ b/mask-parser/src/parser.rs
@@ -56,9 +56,11 @@ pub fn parse(maskfile_contents: String) -> Maskfile {
             }
             End(tag) => match tag {
                 Tag::Header(_) => {
-                    let (name, required_args) = parse_command_name_and_required_args(text.clone());
+                    let (name, required_args, optional_args) =
+                        parse_command_name_required_and_optional_args(text.clone());
                     current_command.name = name;
                     current_command.required_args = required_args;
+                    current_command.optional_args = optional_args;
                 }
                 Tag::BlockQuote => {
                     current_command.description = text.clone();
@@ -230,23 +232,37 @@ fn treeify_commands(commands: Vec<Command>) -> Vec<Command> {
     command_tree
 }
 
-fn parse_command_name_and_required_args(text: String) -> (String, Vec<RequiredArg>) {
-    // Find any required arguments. They look like this: (required_arg_name)
-    let name_and_args: Vec<&str> = text.split(|c| c == '(' || c == ')').collect();
-    let (name, args) = name_and_args.split_at(1);
-    let name = name.join(" ").trim().to_string();
-    let mut required_args: Vec<RequiredArg> = vec![];
-
-    if !args.is_empty() {
-        let args = args.join("");
-        let args: Vec<&str> = args.split(" ").collect();
-        required_args = args
-            .iter()
-            .map(|a| RequiredArg::new(a.to_string()))
-            .collect();
-    }
-
-    (name, required_args)
+fn parse_command_name_required_and_optional_args(
+    text: String,
+) -> (String, Vec<RequiredArg>, Vec<OptionalArg>) {
+    // Checks if any args are present and if not, return early
+    let split_idx = match text.find(|c| c == '(' || c == '[') {
+        Some(idx) => idx,
+        None => return (text.trim().to_string(), vec![], vec![]),
+    };
+
+    let (name, args) = text.split_at(split_idx);
+    let name = name.trim().to_string();
+
+    // Collects (required_args)
+    let required_args = args
+        .split(|c| c == '(' || c == ')')
+        .filter_map(|arg| match arg.trim() {
+            a if !a.is_empty() && !a.contains('[') => Some(RequiredArg::new(a.trim().to_string())),
+            _ => None,
+        })
+        .collect();
+
+    // Collects [optional_args]
+    let optional_args = args
+        .split(|c| c == '[' || c == ']')
+        .filter_map(|arg| match arg.trim() {
+            a if !a.is_empty() && !a.contains('(') => Some(OptionalArg::new(a.trim().to_string())),
+            _ => None,
+        })
+        .collect();
+
+    (name, required_args, optional_args)
 }
 
 #[cfg(test)]
@@ -285,6 +301,18 @@ echo hey
 ## no_script
 
 This command has no source/script.
+
+## multi (required) [optional]
+
+> Example with optional args
+
+~~~bash
+if ! [ -z "$optional" ]; then
+ echo "This is optional - $optional"
+fi
+
+echo "This is required - $required"
+~~~
 "#;
 
 #[cfg(test)]
@@ -327,6 +355,7 @@ mod parse {
                                 "name": "port"
                             }
                         ],
+                        "optional_args": [],
                         "named_flags": [verbose_flag],
                     },
                     {
@@ -343,6 +372,7 @@ mod parse {
                                 "name": "name"
                             }
                         ],
+                        "optional_args": [],
                         "named_flags": [verbose_flag],
                     },
                     {
@@ -360,12 +390,27 @@ mod parse {
                                     "source": "echo hey\n",
                                 },
                                 "subcommands": [],
+                                "optional_args": [],
                                 "required_args": [],
                                 "named_flags": [verbose_flag],
                             }
                         ],
                         "required_args": [],
+                        "optional_args": [],
                         "named_flags": [],
+                    },
+                    {
+                        "level": 2,
+                        "name": "multi",
+                        "description": "Example with optional args",
+                        "script": {
+                            "executor": "bash",
+                            "source": "if ! [ -z \"$optional\" ]; then\n echo \"This is optional - $optional\"\nfi\n\necho \"This is required - $required\"\n",
+                        },
+                        "subcommands": [],
+                        "required_args": [{ "name": "required" }],
+                        "optional_args": [{ "name": "optional" }],
+                        "named_flags": [verbose_flag],
                     }
                 ]
             }),
diff --git a/mask/src/executor.rs b/mask/src/executor.rs
index 10d26b6..c58e52a 100644
--- a/mask/src/executor.rs
+++ b/mask/src/executor.rs
@@ -120,6 +120,11 @@ fn add_flag_variables(mut child: process::Command, cmd: &Command) -> process::Co
         child.env(arg.name.clone(), arg.val.clone());
     }
 
+    // Add all optional args
+    for opt_arg in &cmd.optional_args {
+        child.env(opt_arg.name.clone(), opt_arg.val.clone());
+    }
+
     // Add all named flags as environment variables if they have a value
     for flag in &cmd.named_flags {
         if flag.val != "" {
diff --git a/mask/src/main.rs b/mask/src/main.rs
index cb6f6ea..613d23b 100644
--- a/mask/src/main.rs
+++ b/mask/src/main.rs
@@ -132,6 +132,12 @@ fn build_subcommands<'a, 'b>(
             subcmd = subcmd.arg(arg);
         }
 
+        // Add all optional arguments
+        for o in &c.optional_args {
+            let arg = Arg::with_name(&o.name);
+            subcmd = subcmd.arg(arg);
+        }
+
         // Add all named flags
         for f in &c.named_flags {
             let arg = Arg::with_name(&f.name)
@@ -174,6 +180,14 @@ fn get_command_options(mut cmd: Command, matches: &ArgMatches) -> Command {
         arg.val = matches.value_of(arg.name.clone()).unwrap().to_string();
     }
 
+    // Check optional args
+    for opt_arg in &mut cmd.optional_args {
+        opt_arg.val = matches
+            .value_of(opt_arg.name.clone())
+            .unwrap_or("")
+            .to_string();
+    }
+
     // Check all named flags
     for flag in &mut cmd.named_flags {
         flag.val = if flag.takes_value {
diff --git a/mask/tests/arguments_and_flags_test.rs b/mask/tests/arguments_and_flags_test.rs
index d3bbb74..e78d1a9 100644
--- a/mask/tests/arguments_and_flags_test.rs
+++ b/mask/tests/arguments_and_flags_test.rs
@@ -510,3 +510,68 @@ Write-Output "This shouldn't render"
             .failure();
     }
 }
+
+mod optional_args {
+    use predicates::boolean::PredicateBooleanExt;
+
+    use super::*;
+
+    #[test]
+    fn runs_with_optional_args() {
+        let (_temp, maskfile_path) = common::maskfile(
+            r#"
+## with_opt (required) [optional]
+
+~~~bash
+echo "$required" "$optional"
+~~~
+
+~~~powershell
+param(
+    $req = $env:required,
+    $opt = $env:optional
+)
+
+Write-Output "$req $opt"
+~~~
+"#,
+        );
+
+        common::run_mask(&maskfile_path)
+            .cli("with_opt")
+            .arg("I am required")
+            .arg("I am optional")
+            .assert()
+            .stdout(contains("I am required I am optional"))
+            .success();
+    }
+
+    #[test]
+    fn does_not_fail_when_optional_arg_is_not_present() {
+        let (_temp, maskfile_path) = common::maskfile(
+            r#"
+## with_opt (required) [optional]
+
+~~~bash
+echo "$required" "$optional"
+~~~
+
+~~~powershell
+param(
+    $req = $env:required,
+    $opt = $env:optional
+)
+
+Write-Output "$req $opt"
+~~~
+"#,
+        );
+
+        common::run_mask(&maskfile_path)
+            .cli("with_opt")
+            .arg("I am required")
+            .assert()
+            .stdout(contains("I am optional").not())
+            .success();
+    }
+}
diff --git a/mask/tests/introspect_test.rs b/mask/tests/introspect_test.rs
index 7c2a88f..a343b70 100644
--- a/mask/tests/introspect_test.rs
+++ b/mask/tests/introspect_test.rs
@@ -44,6 +44,7 @@ echo something
                 },
                 "subcommands": [],
                 "required_args": [],
+                "optional_args": [],
                 "named_flags": [verbose_flag],
             }
         ]