diff --git a/cli/teos_cli.py b/cli/teos_cli.py
index aee10c31..0b3b8099 100644
--- a/cli/teos_cli.py
+++ b/cli/teos_cli.py
@@ -200,6 +200,46 @@ def get_all_appointments(teos_url):
         return None
 
 
+def delete_appointment(locator, cli_sk, teos_pk, teos_url):
+    """
+    Deletes information about an appointment from the tower.
+
+    Args:
+        locator (:obj:`str`): the locator used to identify the appointment.
+        cli_sk (:obj:`PrivateKey`): the client's private key.
+        teos_pk (:obj:`PublicKey`): the tower's public key.
+        teos_url (:obj:`str`): the teos base url.
+
+    Returns:
+        :obj:`dict` or :obj:`None`: a dictionary containing the appointment data if the locator is valid and the tower
+        responds. ``None`` otherwise.
+
+    Raises:
+        :obj:`InvalidParameter <cli.exceptions.InvalidParameter>`: if ``locator`` is invalid.
+        :obj:`ConnectionError`: if the client cannot connect to the tower.
+        :obj:`TowerResponseError <cli.exceptions.TowerResponseError>`: if the tower responded with an error, or the
+        response was invalid.
+    """
+
+    # FIXME: All responses from the tower should be signed. Not using teos_pk atm.
+
+    if not is_locator(locator):
+        raise InvalidParameter("The provided locator is not valid", locator=locator)
+
+    message = "delete appointment {}".format(locator)
+    signature = Cryptographer.sign(message.encode(), cli_sk)
+    data = {"locator": locator, "signature": signature}
+
+    # Send request to the server.
+    delete_appointment_endpoint = "{}/delete_appointment".format(teos_url)
+    logger.info("Sending appointment deletion request to the Eye of Satoshi")
+    server_response = post_request(data, delete_appointment_endpoint)
+
+    response_json = process_post_response(server_response)
+
+    return response_json
+
+
 def load_keys(teos_pk_path, user_sk_path):
     """
     Loads all the keys required so sign, send, and verify the appointment.
diff --git a/teos/api.py b/teos/api.py
index b1c90ecc..970e0187 100644
--- a/teos/api.py
+++ b/teos/api.py
@@ -5,8 +5,8 @@
 from teos import LOG_PREFIX
 import common.errors as errors
 from teos.inspector import InspectionFailed
-from teos.watcher import AppointmentLimitReached, AppointmentAlreadyTriggered
 from teos.gatekeeper import NotEnoughSlots, AuthenticationFailure
+from teos.watcher import AppointmentLimitReached, AppointmentAlreadyTriggered, AppointmentNotFound
 
 from common.logger import Logger
 from common.cryptographer import hash_160
@@ -87,6 +87,7 @@ def __init__(self, host, port, inspector, watcher):
             "/add_appointment": (self.add_appointment, ["POST"]),
             "/get_appointment": (self.get_appointment, ["POST"]),
             "/get_all_appointments": (self.get_all_appointments, ["GET"]),
+            "/delete_appointment": (self.delete_appointment, ["POST"]),
         }
 
         for url, params in routes.items():
@@ -300,6 +301,78 @@ def get_all_appointments(self):
 
         return response
 
+    def delete_appointment(self):
+        """
+        Delete information about a given appointment state in the Watchtower.
+
+        The information is requested by ``locator``.
+
+        Returns:
+            :obj:`str`: A json formatted dictionary containing information about the appointment deletion request.
+
+            Returns not found if the user does not have the requested appointment or the locator is invalid.
+            Returns bad request if the appointment does not exist in the Watchtower.
+
+            A ``status`` flag is added to the data that signals the status of the deletion request.
+
+            - A successfully deleted appointment is flagged as ``deletion_accepted``.
+            - An appointment that did not exist (or was already deleted), or where the locator is invalid or the user
+            does not have the requested appointment, are flagged as ``deletion_rejected``.
+
+            :obj:`tuple`: A tuple containing the response (:obj:`str`) and response code (:obj:`int`). For accepted
+            appointments, the ``rcode`` is always 200 and the response contains the receipt signature (json). For
+            rejected appointments, the ``rcode`` is either 400 or 404:
+
+            If the appointment is not found: 404
+            If the request is invalid: 400
+            If the appointment is already in the responder: 400 + message
+        """
+
+        # Getting the real IP if the server is behind a reverse proxy
+        remote_addr = get_remote_addr()
+
+        # Check that data type and content are correct. Abort otherwise.
+        try:
+            request_data = get_request_data_json(request)
+
+        except InvalidParameter as e:
+            logger.info("Received invalid delete_appointment request", from_addr="{}".format(remote_addr))
+            return jsonify({"error": str(e), "error_code": errors.INVALID_REQUEST_FORMAT}), HTTP_BAD_REQUEST
+
+        locator = request_data.get("locator")
+
+        try:
+            self.inspector.check_locator(locator)
+            logger.info("Received delete_appointment request", from_addr=remote_addr, locator=locator)
+
+            message = "delete appointment {}".format(locator).encode()
+            user_signature = request_data.get("signature")
+            user_id = self.watcher.gatekeeper.authenticate_user(message, user_signature)
+
+            tower_signature = self.watcher.pop_appointment(locator, user_id, user_signature)
+
+            rcode = HTTP_OK
+            response = {
+                "locator": locator,
+                "signature": tower_signature,
+                "available_slots": self.watcher.gatekeeper.registered_users[user_id].get("available_slots"),
+                "status": "deletion_accepted",
+            }
+
+        except AppointmentNotFound:
+            rcode = HTTP_NOT_FOUND
+            response = {"locator": locator, "status": "deletion_rejected"}
+
+        except AppointmentAlreadyTriggered as e:
+            rcode = HTTP_BAD_REQUEST
+            response = {"locator": locator, "status": "deletion_rejected", "error": e.msg}
+
+        except (InspectionFailed, AuthenticationFailure):
+            rcode = HTTP_BAD_REQUEST
+            response = {"locator": locator, "status": "deletion_rejected"}
+
+        return jsonify(response), rcode
+
     def start(self):
         """ This function starts the Flask server used to run the API """
 
diff --git a/teos/watcher.py b/teos/watcher.py
index 644bc79c..9355face 100644
--- a/teos/watcher.py
+++ b/teos/watcher.py
@@ -1,5 +1,5 @@
 from queue import Queue
-from threading import Thread
+from threading import Thread, Lock
 from collections import OrderedDict
 from readerwriterlock import rwlock
 
@@ -22,6 +22,10 @@ class AppointmentLimitReached(BasicException):
     """Raised when the tower maximum appointment count has been reached"""
 
 
+class AppointmentNotFound(BasicException):
+    """Raised when an appointment is not found in the tower"""
+
+
 class AppointmentAlreadyTriggered(BasicException):
     """Raised when an appointment is sent to the Watcher but that same data has already been sent to the Responder"""
 
@@ -335,6 +339,51 @@ def add_appointment(self, appointment, signature):
             "subscription_expiry": self.gatekeeper.registered_users[user_id].subscription_expiry,
         }
 
+    def delete_appointment(self, locator, user_id, user_signature):
+        """
+        Deletes an appointment from the ``Watcher``. The tower will stop monitoring the deleted appointment.
+
+        Args:
+            locator (:obj:`str`): a 16-byte hex string identifying the appointment.
+            user_id (:obj:`str`): the public key that identifies the user who request the deletion (33-bytes hex str).
+            user_signature (:obj:`str`): the signature of the request provided by the user. The tower will sign the
+                signature deletion is accepted.
+
+        Returns:
+            :obj:`str`: the signature of the user's signature if the appointment if the deletion is accepted.
+
+        Rises:
+            :obj:`AppointmentAlreadyTriggered`: if the appointment is already in the Responder. The deletion is
+            therefore rejected.
+            :obj:`AppointmentNotFound`: if the appointment cannot be found in the tower. The deletion is therefore
+            rejected.
+        """
+
+        uuid = hash_160("{}{}".format(locator, user_id))
+
+        # FIXME: We need to keep track of deletions
+
+        if uuid in self.appointments:
+            # Delete the appointment from both the Watcher and the Gatekeeper
+            Cleaner.delete_completed_appointments([uuid], self.appointments, self.locator_uuid_map, self.db_manager)
+            Cleaner.delete_gatekeeper_appointments(self.gatekeeper, {uuid: user_id})
+
+            # Sign over the user signature as acceptance of the deletion request.
+            signature = Cryptographer.sign(user_signature.encode(), self.signing_key)
+            logger.info("Appointment deleted", locator=locator)
+
+            return signature
+
+        elif uuid in self.responder.trackers:
+            message = "Cannot delete an already triggered appointment"
+            logger.info(message, locator=locator)
+            raise AppointmentAlreadyTriggered(message)
+
+        else:
+            message = "Appointment not found. Deletion rejected"
+            logger.info(message, locator=locator)
+            raise AppointmentNotFound(message)
+
     def do_watch(self):
         """
         Monitors the blockchain for channel breaches.