diff --git a/HISTORY.rst b/HISTORY.rst
index f05a4637..d0dd63ad 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -11,6 +11,7 @@ PlatformIO Core 5
 5.2.3 (2021-??-??)
 ~~~~~~~~~~~~~~~~~~
 
+- Added support for custom `device monitor filters <https://docs.platformio.org/page/core/userguide/device/cmd_monitor.html#filters>`__ (`issue #3924 <https://github.com/platformio/platformio-core/issues/3924>`_)
 - Show human-readable message when infinite recursion is detected while processing `Interpolation of Values <https://docs.platformio.org/page/projectconf/interpolation.html>`__ (`issue #3883 <https://github.com/platformio/platformio-core/issues/3883>`_)
 - Improved directory interpolation (``${platformio.***_dir}``) in `"platformio.ini" <https://docs.platformio.org/page/projectconf.html>`__ configuration file (`issue #3934 <https://github.com/platformio/platformio-core/issues/3934>`_)
 - Ignore resolving of SCons variables (e.g., ``${(SOURCE.get_abspath())}``) when preprocessing interpolations (`issue #3933 <https://github.com/platformio/platformio-core/issues/3933>`_)
diff --git a/docs b/docs
index 2f0abf6a..7e751e69 160000
--- a/docs
+++ b/docs
@@ -1 +1 @@
-Subproject commit 2f0abf6aba38c9310b08fd5200ed36eeacbfdb5a
+Subproject commit 7e751e6990958ca6b8120f37b2405a41f0b5b72d
diff --git a/platformio/commands/device/command.py b/platformio/commands/device/command.py
index 1f386438..1cf0b265 100644
--- a/platformio/commands/device/command.py
+++ b/platformio/commands/device/command.py
@@ -23,6 +23,7 @@ from serial.tools import miniterm
 from platformio import exception, fs, util
 from platformio.commands.device import helpers as device_helpers
 from platformio.platform.factory import PlatformFactory
+from platformio.project.config import ProjectConfig
 from platformio.project.exception import NotPlatformIOProjectError
 
 
@@ -182,19 +183,25 @@ def device_monitor(**kwargs):  # pylint: disable=too-many-branches
         )
 
     project_options = {}
+    platform = None
     try:
         with fs.cd(kwargs["project_dir"]):
             project_options = device_helpers.get_project_options(kwargs["environment"])
-        kwargs = device_helpers.apply_project_monitor_options(kwargs, project_options)
+            device_helpers.register_filters(
+                ProjectConfig.get_instance().get("platformio", "monitor_dir"),
+                options=kwargs,
+            )
+            if "platform" in project_options:
+                platform = PlatformFactory.new(project_options["platform"])
+                device_helpers.register_filters(
+                    os.path.join(platform.get_dir(), "monitor"), options=kwargs
+                )
+            kwargs = device_helpers.apply_project_monitor_options(
+                kwargs, project_options
+            )
     except NotPlatformIOProjectError:
         pass
 
-    platform = None
-    if "platform" in project_options:
-        with fs.cd(kwargs["project_dir"]):
-            platform = PlatformFactory.new(project_options["platform"])
-            device_helpers.register_platform_filters(platform, options=kwargs)
-
     if not kwargs["port"]:
         ports = util.get_serial_ports(filter_hwid=True)
         if len(ports) == 1:
diff --git a/platformio/commands/device/helpers.py b/platformio/commands/device/helpers.py
index a65b4895..8b4b789c 100644
--- a/platformio/commands/device/helpers.py
+++ b/platformio/commands/device/helpers.py
@@ -92,11 +92,9 @@ def load_monitor_filter(path, options=None):
     return True
 
 
-def register_platform_filters(platform, options=None):
-    monitor_dir = os.path.join(platform.get_dir(), "monitor")
+def register_filters(monitor_dir, options=None):
     if not os.path.isdir(monitor_dir):
         return
-
     for name in os.listdir(monitor_dir):
         if not name.startswith("filter_") or not name.endswith(".py"):
             continue
diff --git a/platformio/project/options.py b/platformio/project/options.py
index f94a74c6..c8a46da9 100644
--- a/platformio/project/options.py
+++ b/platformio/project/options.py
@@ -314,11 +314,19 @@ ProjectOptions = OrderedDict(
             ConfigPlatformioOption(
                 group="directory",
                 name="boards_dir",
-                description="A global storage for custom board manifests",
+                description="A storage for custom board manifests",
                 sysenvvar="PLATFORMIO_BOARDS_DIR",
                 default=os.path.join("$PROJECT_DIR", "boards"),
                 validate=validate_dir,
             ),
+            ConfigPlatformioOption(
+                group="directory",
+                name="monitor_dir",
+                description="A storage for custom monitor filters",
+                sysenvvar="PLATFORMIO_MONITOR_DIR",
+                default=os.path.join("$PROJECT_DIR", "monitor"),
+                validate=validate_dir,
+            ),
             ConfigPlatformioOption(
                 group="directory",
                 name="shared_dir",