diff --git a/CMakeLists.txt b/CMakeLists.txt
index e59eb4c5f..acc061fcf 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -168,7 +168,7 @@ if(FSFW_BUILD_TESTS)
   configure_file(unittests/testcfg/TestsConfig.h.in tests/TestsConfig.h)
 
   project(${FSFW_TEST_TGT} CXX C)
-  add_executable(${FSFW_TEST_TGT})
+  add_executable(${FSFW_TEST_TGT} unittests/tmtcpacket/testCcsds.cpp)
   if(IPO_SUPPORTED AND FSFW_ENABLE_IPO)
     set_property(TARGET ${FSFW_TEST_TGT} PROPERTY INTERPROCEDURAL_OPTIMIZATION
                                                   TRUE)
diff --git a/src/fsfw/tmtcpacket/ccsds/PacketId.h b/src/fsfw/tmtcpacket/ccsds/PacketId.h
index 29b82f138..2c77652c2 100644
--- a/src/fsfw/tmtcpacket/ccsds/PacketId.h
+++ b/src/fsfw/tmtcpacket/ccsds/PacketId.h
@@ -42,8 +42,20 @@ struct PacketId : public SerializeIF {
 
   ReturnValue_t serialize(uint8_t **buffer, size_t *size, size_t maxSize,
                           Endianness streamEndianness) const override {
-    uint16_t pscRaw = raw();
-    return SerializeAdapter::serialize(&pscRaw, buffer, size, maxSize, streamEndianness);
+    if (*size + getSerializedSize() > maxSize) {
+      return SerializeIF::BUFFER_TOO_SHORT;
+    }
+    uint16_t idRaw = raw();
+    // Leave the first three bits untouched, they could generally contain the CCSDS version,
+    // or more generally, the packet ID is a 13 bit field
+    **buffer &= ~0x1f;
+    **buffer |= (idRaw >> 8) & 0x1f;
+    *size += 1;
+    *buffer += 1;
+    **buffer = idRaw & 0xff;
+    *size += 1;
+    *buffer += 1;
+    return HasReturnvaluesIF::RETURN_OK;
   }
 
   [[nodiscard]] size_t getSerializedSize() const override { return 2; }
diff --git a/unittests/tmtcpacket/CMakeLists.txt b/unittests/tmtcpacket/CMakeLists.txt
index f47c63704..dd0100a60 100644
--- a/unittests/tmtcpacket/CMakeLists.txt
+++ b/unittests/tmtcpacket/CMakeLists.txt
@@ -5,4 +5,5 @@ target_sources(${FSFW_TEST_TGT} PRIVATE
   testPusTcReader.cpp
   testPusTmCreator.cpp
   testPusTmReader.cpp
+  testCcsds.cpp
 )
diff --git a/unittests/tmtcpacket/testCcsds.cpp b/unittests/tmtcpacket/testCcsds.cpp
new file mode 100644
index 000000000..28b255e5b
--- /dev/null
+++ b/unittests/tmtcpacket/testCcsds.cpp
@@ -0,0 +1,53 @@
+#include <array>
+#include <catch2/catch_test_macros.hpp>
+
+#include "fsfw/tmtcpacket/ccsds/PacketId.h"
+#include "fsfw/tmtcpacket/ccsds/header.h"
+
+TEST_CASE("CCSDS Low Level", "[ccsds-ll]") {
+  SECTION("Lowlevel Header Packet ID test") {
+    ccsds::PrimaryHeader header{};
+    uint16_t packetIdRaw = 0x3ff;
+    ccsds::setPacketId(header, packetIdRaw);
+    REQUIRE(header.packetIdHAndVersion == 3);
+    REQUIRE(header.packetIdL == 0xff);
+    REQUIRE(ccsds::getPacketId(header) == 0x3ff);
+    header.packetIdHAndVersion |= 0b00100000;
+    REQUIRE(ccsds::getPacketId(header) == 0x3ff);
+    REQUIRE(ccsds::getVersion(header) == 0b001);
+  }
+
+  SECTION("Lowlevel Header APID Test") {
+    ccsds::PrimaryHeader header{};
+    uint16_t packetIdRaw = 0x3ff;
+    ccsds::setPacketId(header, packetIdRaw);
+    ccsds::setApid(header, 0x1ff);
+    REQUIRE(ccsds::getPacketId(header) == 0x1ff);
+  }
+
+  SECTION("Lowlevel Packet Length Test") {
+    ccsds::PrimaryHeader header{};
+    header.packetLenH = 0x02;
+    header.packetLenL = 0x03;
+    REQUIRE(ccsds::getPacketLen(header) == 0x0203);
+  }
+}
+
+TEST_CASE("CCSDS Packet ID", "[ccsds-packet-id]") {
+  PacketId packetId;
+  std::array<uint8_t, 3> buf{};
+  size_t serLen = 0;
+  uint8_t* ptr = buf.data();
+  SECTION("Basic") {
+    packetId.apid = 0x1ff;
+    packetId.secHeaderFlag = false;
+    packetId.packetType = ccsds::PacketType::TM;
+    REQUIRE(packetId.raw() == 0x1ff);
+    REQUIRE(packetId.serialize(&ptr, &serLen, buf.size(), SerializeIF::Endianness::NETWORK) ==
+            HasReturnvaluesIF::RETURN_OK);
+    REQUIRE(buf[0] == 0x1);
+    REQUIRE(buf[1] == 0xff);
+  }
+}
+
+TEST_CASE("CCSDS Packet Seq Ctrl", "[ccsds-packet-seq-ctrl]") {}