diff --git a/src/odb/include/odb/3dblox.h b/src/odb/include/odb/3dblox.h
index b6e07ff5626..ebe0eb33c6e 100644
--- a/src/odb/include/odb/3dblox.h
+++ b/src/odb/include/odb/3dblox.h
@@ -69,5 +69,6 @@ class ThreeDBlox
   std::unordered_set<odb::dbTech*> written_techs_;
   std::unordered_set<odb::dbLib*> written_libs_;
   std::unordered_set<std::string> read_files_;
+  std::unordered_set<odb::dbChip*> insts_with_def_;
 };
 }  // namespace odb
diff --git a/src/odb/src/3dblox/3dblox.cpp b/src/odb/src/3dblox/3dblox.cpp
index 5c10e56a4f6..a4dd18cfd5b 100644
--- a/src/odb/src/3dblox/3dblox.cpp
+++ b/src/odb/src/3dblox/3dblox.cpp
@@ -398,6 +398,20 @@ static std::string getFileName(const std::string& tech_file_path)
   return tech_file_path_fs.stem().string();
 }
 
+static inline void readDefForChip(odb::dbDatabase* db,
+                                  utl::Logger* logger,
+                                  odb::dbChip* chip,
+                                  const std::string& def_file)
+{
+  odb::defin def_reader(db, logger, odb::defin::DEFAULT);
+  std::vector<odb::dbLib*> search_libs;
+  for (odb::dbLib* lib : db->getLibs()) {
+    search_libs.push_back(lib);
+  }
+  // No callbacks here as we are going to give one postRead3Dbx later
+  def_reader.readChip(search_libs, def_file.c_str(), chip, false);
+}
+
 void ThreeDBlox::createChiplet(const ChipletDef& chiplet)
 {
   dbTech* tech = nullptr;
@@ -454,16 +468,7 @@ void ThreeDBlox::createChiplet(const ChipletDef& chiplet)
 
   // Read DEF file
   if (!chiplet.external.def_file.empty()) {
-    odb::defin def_reader(db_, logger_, odb::defin::DEFAULT);
-    std::vector<odb::dbLib*> search_libs;
-    for (odb::dbLib* lib : db_->getLibs()) {
-      search_libs.push_back(lib);
-    }
-    // No callbacks here as we are going to give one postRead3Dbx later
-    def_reader.readChip(search_libs,
-                        chiplet.external.def_file.c_str(),
-                        chip,
-                        /*issue_callback*/ false);
+    readDefForChip(db_, logger_, chip, chiplet.external.def_file);
   }
   const int dbu_per_micron = db_->getDbuPerMicron();
   if (chiplet.design_width != -1.0) {
@@ -677,6 +682,22 @@ void ThreeDBlox::createChipInst(const ChipletInst& chip_inst)
                    chip_inst.reference,
                    chip_inst.name);
   }
+
+  if (!chip_inst.external.def_file.empty()) {
+    if (insts_with_def_.contains(chip)) {
+      logger_->error(utl::ODB,
+                     546,
+                     "3DBX Parser Error: There can't be 2 instances of the "
+                     "same chiplet {} with a def file each",
+                     chip->getName());
+    }
+    insts_with_def_.insert(chip);
+    if (chip->getBlock() != nullptr) {
+      odb::dbBlock::destroy(chip->getBlock());
+    }
+    readDefForChip(db_, logger_, chip, chip_inst.external.def_file);
+  }
+
   dbChipInst* inst = dbChipInst::create(db_->getChip(), chip, chip_inst.name);
   auto orient_str = chip_inst.orient;
   if (dup_orient_map.contains(orient_str)) {
diff --git a/src/odb/src/3dblox/dbxWriter.cpp b/src/odb/src/3dblox/dbxWriter.cpp
index 39684afd5f8..fbce5ad86be 100644
--- a/src/odb/src/3dblox/dbxWriter.cpp
+++ b/src/odb/src/3dblox/dbxWriter.cpp
@@ -21,6 +21,7 @@ DbxWriter::DbxWriter(utl::Logger* logger, odb::dbDatabase* db)
 
 void DbxWriter::writeChiplet(const std::string& filename, odb::dbChip* chiplet)
 {
+  written_def_chips_.clear();
   YAML::Node root;
   writeYamlContent(root, chiplet);
   writeYamlToFile(filename, root);
@@ -65,8 +66,15 @@ void DbxWriter::writeChipletInsts(YAML::Node& instances_node,
 void DbxWriter::writeChipletInst(YAML::Node& instance_node,
                                  odb::dbChipInst* inst)
 {
-  auto master_name = inst->getMasterChip()->getName();
+  auto chip = inst->getMasterChip();
+  auto master_name = chip->getName();
   instance_node["reference"] = master_name;
+
+  if (written_def_chips_.find(chip) == written_def_chips_.end()) {
+    YAML::Node external_node = instance_node["external"];
+    external_node["def_file"] = std::string(master_name) + ".def";
+    written_def_chips_.insert(chip);
+  }
 }
 
 void DbxWriter::writeStack(YAML::Node& stack_node, odb::dbChip* chiplet)
diff --git a/src/odb/src/3dblox/dbxWriter.h b/src/odb/src/3dblox/dbxWriter.h
index dbe33ed0506..f8faf10f2ad 100644
--- a/src/odb/src/3dblox/dbxWriter.h
+++ b/src/odb/src/3dblox/dbxWriter.h
@@ -4,6 +4,7 @@
 #pragma once
 
 #include <string>
+#include <unordered_set>
 #include <vector>
 
 #include "baseWriter.h"
@@ -42,6 +43,8 @@ class DbxWriter : public BaseWriter
   void writeConnection(YAML::Node& connection_node, odb::dbChipConn* conn);
   std::string buildPath(const std::vector<dbChipInst*>& path_insts,
                         odb::dbChipRegionInst* region);
+
+  std::unordered_set<odb::dbChip*> written_def_chips_;
 };
 
 }  // namespace odb
\ No newline at end of file