diff --git a/src/posix/platform/radio.cpp b/src/posix/platform/radio.cpp
index 4d30f54e2..faefa6758 100644
--- a/src/posix/platform/radio.cpp
+++ b/src/posix/platform/radio.cpp
@@ -99,6 +99,7 @@ void platformRadioInit(otUrl *aRadioUrl)
     ot::Posix::RadioUrl &radioUrl       = *static_cast<ot::Posix::RadioUrl *>(aRadioUrl);
     bool                 resetRadio     = (radioUrl.GetValue("no-reset") == nullptr);
     bool                 restoreDataset = (radioUrl.GetValue("ncp-dataset") != nullptr);
+    const char *         urlFemLnaGain  = radioUrl.GetValue("fem-lnagain");
 #if OPENTHREAD_POSIX_CONFIG_MAX_POWER_TABLE_ENABLE
     uint8_t     channel       = ot::Radio::kChannelMin;
     int8_t      power         = ot::Posix::MaxPowerTable::kPowerDefault;
@@ -128,6 +129,14 @@ void platformRadioInit(otUrl *aRadioUrl)
 
     SuccessOrDie(sRadioSpinel.GetSpinelInterface().Init(radioUrl));
     sRadioSpinel.Init(resetRadio, restoreDataset);
+
+    if (urlFemLnaGain != nullptr)
+    {
+        long femLnaGain = strtol(urlFemLnaGain, nullptr, 0);
+
+        VerifyOrDie(INT8_MIN <= femLnaGain && femLnaGain <= INT8_MAX, OT_EXIT_INVALID_ARGUMENTS);
+        SuccessOrDie(sRadioSpinel.SetFemLnaGain(static_cast<int8_t>(femLnaGain)));
+    }
 }
 
 void platformRadioDeinit(void)
diff --git a/src/posix/platform/radio_url.cpp b/src/posix/platform/radio_url.cpp
index e28705868..7dbc84d39 100644
--- a/src/posix/platform/radio_url.cpp
+++ b/src/posix/platform/radio_url.cpp
@@ -66,14 +66,14 @@ const char *otSysGetRadioUrlHelpString(void)
 #else
 
 #define OT_RADIO_URL_HELP_BUS                                                                        \
+    "    forkpty-arg[=argument string]  Command line arguments for subprocess, can be repeated.\n"   \
     "    spinel+hdlc+uart://${PATH_TO_UART_DEVICE}?${Parameters} for real uart device\n"             \
     "    spinel+hdlc+forkpty://${PATH_TO_UART_DEVICE}?${Parameters} for forking a pty subprocess.\n" \
     "Parameters:\n"                                                                                  \
     "    uart-parity[=even|odd]         Uart parity config, optional.\n"                             \
     "    uart-stop[=number-of-bits]     Uart stop bit, default is 1.\n"                              \
     "    uart-baudrate[=baudrate]       Uart baud rate, default is 115200.\n"                        \
-    "    uart-flow-control              Enable flow control, disabled by default.\n"                 \
-    "    forkpty-arg[=argument string]  Command line arguments for subprocess, can be repeated.\n"
+    "    uart-flow-control              Enable flow control, disabled by default.\n"
 
 #endif // OPENTHREAD_POSIX_CONFIG_RCP_BUS == OT_POSIX_RCP_BUS_SPI
 
@@ -88,8 +88,9 @@ const char *otSysGetRadioUrlHelpString(void)
 #endif
 
     return "RadioURL:\n" OT_RADIO_URL_HELP_BUS OT_RADIO_URL_HELP_MAX_POWER_TABLE
-           "    no-reset                      Do not send Spinel reset command to RCP on initialization.\n"
-           "    ncp-dataset                   Retrieve dataset from ncp.\n";
+           "    fem-lnagain[=dbm]             Set the Rx LNA gain in dBm of the external FEM.\n"
+           "    ncp-dataset                   Retrieve dataset from ncp.\n"
+           "    no-reset                      Do not send Spinel reset command to RCP on initialization.\n";
 }
 
 namespace ot {
diff --git a/tests/scripts/expect/posix-fem-lnagain.exp b/tests/scripts/expect/posix-fem-lnagain.exp
new file mode 100755
index 000000000..77adfaa4c
--- /dev/null
+++ b/tests/scripts/expect/posix-fem-lnagain.exp
@@ -0,0 +1,54 @@
+#!/usr/bin/expect -f
+#
+#  Copyright (c) 2020, The OpenThread Authors.
+#  All rights reserved.
+#
+#  Redistribution and use in source and binary forms, with or without
+#  modification, are permitted provided that the following conditions are met:
+#  1. Redistributions of source code must retain the above copyright
+#     notice, this list of conditions and the following disclaimer.
+#  2. Redistributions in binary form must reproduce the above copyright
+#     notice, this list of conditions and the following disclaimer in the
+#     documentation and/or other materials provided with the distribution.
+#  3. Neither the name of the copyright holder nor the
+#     names of its contributors may be used to endorse or promote products
+#     derived from this software without specific prior written permission.
+#
+#  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+#  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+#  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+#  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+#  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+#  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+#  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+#  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+#  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+#  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+#  POSSIBILITY OF SUCH DAMAGE.
+#
+
+spawn $env(OT_POSIX_APPS)/ot-cli "spinel+hdlc+uart://$env(OT_SIMULATION_APPS)/ncp/ot-rcp?forkpty-arg=1&fem-lnagain=10"
+expect_after {
+    timeout { exit 1 }
+}
+send "fem lnagain\n"
+expect "10"
+expect "Done"
+send "\x04"
+expect eof
+
+spawn $env(OT_POSIX_APPS)/ot-cli "spinel+hdlc+uart://$env(OT_SIMULATION_APPS)/ncp/ot-rcp?forkpty-arg=1&fem-lnagain=-128"
+expect_after {
+    timeout { exit 1 }
+}
+send "fem lnagain\n"
+expect -- "-128"
+expect "Done"
+send "\x04"
+expect eof
+
+spawn $env(OT_POSIX_APPS)/ot-cli "spinel+hdlc+uart://$env(OT_SIMULATION_APPS)/ncp/ot-rcp?forkpty-arg=1&fem-lnagain=-129"
+expect_after {
+    timeout { exit 1 }
+}
+expect eof