diff --git a/substrate/subkey/README.adoc b/substrate/subkey/README.adoc
index 7fe194eb82..52770e78ec 100644
--- a/substrate/subkey/README.adoc
+++ b/substrate/subkey/README.adoc
@@ -53,3 +53,18 @@ You can use the included vanity generator to find a seed that provides an addres
 ```bash
 subkey vanity 1337
 ```
+
+=== Signing a transaction
+
+Sign a transaction from an encoded `Call`.
+
+```bash
+subkey sign-transaction \
+	--call <call-as-hex> \
+	--nonce 0 \
+	--suri <secret-uri> \
+	--password <password> \
+	--prior-block-hash <prior-block-hash-as-hex>
+```
+
+Will output a signed and encoded `UncheckedMortalCompactExtrinsic` as hex.
diff --git a/substrate/subkey/src/cli.yml b/substrate/subkey/src/cli.yml
index 8b839cd443..eedd475737 100644
--- a/substrate/subkey/src/cli.yml
+++ b/substrate/subkey/src/cli.yml
@@ -92,3 +92,36 @@ subcommands:
             help: Number of keys to generate
             takes_value: true
             default_value: "1"
+  - sign-transaction:
+      about: Sign transaction from encoded Call. Returns a signed and encoded UncheckedMortalCompactExtrinsic as hex.
+      args:
+        - call:
+            short: c
+            long: call
+            help: The call, hex-encoded.
+            takes_value: true
+            required: true
+        - nonce:
+            short: n
+            long: nonce
+            help: The nonce.
+            takes_value: true
+            required: true
+        - suri:
+            long: suri
+            short: s
+            help: The secret key URI.
+            takes_value: true
+            required: true
+        - password:
+            short: p
+            long: password
+            takes_value: true
+            help: The password for the key.
+            required: true
+        - prior-block-hash:
+            short: h
+            long: prior-block-hash
+            help: The prior block hash, hex-encoded.
+            takes_value: true
+            required: true
diff --git a/substrate/subkey/src/main.rs b/substrate/subkey/src/main.rs
index b0ad1b281d..1b9afb8cd7 100644
--- a/substrate/subkey/src/main.rs
+++ b/substrate/subkey/src/main.rs
@@ -223,6 +223,48 @@ fn execute<C: Crypto<Seed=[u8; 32]>>(matches: clap::ArgMatches) where
 			);
 			println!("0x{}", hex::encode(&extrinsic.encode()));
 		}
+		("sign-transaction", Some(matches)) => {
+			let s = matches.value_of("suri")
+				.expect("secret URI parameter is required; thus it can't be None; qed");
+			let signer = Sr25519::pair_from_suri(s, password);
+
+			let index = matches.value_of("nonce")
+				.expect("nonce is required; thus it can't be None; qed");
+			let index = str::parse::<Index>(index)
+				.expect("Invalid 'index' parameter; expecting an integer.");
+
+			let call = matches.value_of("call")
+				.expect("call is required; thus it can't be None; qed");
+			let function: Call = hex::decode(&call).ok()
+				.and_then(|x| Decode::decode(&mut &x[..])).unwrap();
+
+			let h = matches.value_of("prior-block-hash")
+				.expect("prior-block-hash is required; thus it can't be None; qed");
+			let prior_block_hash: Hash = hex::decode(h).ok()
+				.and_then(|x| Decode::decode(&mut &x[..]))
+				.expect("Invalid prior block hash");
+
+			let era = Era::immortal();
+
+			let raw_payload = (Compact(index), function, era, prior_block_hash);
+			let signature = raw_payload.using_encoded(|payload|
+				if payload.len() > 256 {
+					signer.sign(&blake2_256(payload)[..])
+				} else {
+					signer.sign(payload)
+				}
+			);
+
+			let extrinsic = UncheckedExtrinsic::new_signed(
+				index,
+				raw_payload.1,
+				signer.public().into(),
+				signature.into(),
+				era,
+			);
+
+			println!("0x{}", hex::encode(&extrinsic.encode()));
+		}
 		("verify", Some(matches)) => {
 			let sig_data = matches.value_of("sig")
 				.expect("signature parameter is required; thus it can't be None; qed");