diff --git a/cpp/include/cudf/io/types.hpp b/cpp/include/cudf/io/types.hpp
index 23ed0153f3f..9d6a83e8730 100644
--- a/cpp/include/cudf/io/types.hpp
+++ b/cpp/include/cudf/io/types.hpp
@@ -124,7 +124,10 @@ struct table_metadata {
   std::vector<std::string> column_names;  //!< Names of columns contained in the table
   std::vector<column_name_info>
     schema_info;  //!< Detailed name information for the entire output hierarchy
-  std::map<std::string, std::string> user_data;  //!< Format-dependent metadata as key-values pairs
+  std::map<std::string, std::string> user_data;  //!< Format-dependent metadata of the first input
+                                                 //!< file as key-values pairs (deprecated)
+  std::vector<std::unordered_map<std::string, std::string>>
+    per_file_user_data;  //!< Per file format-dependent metadata as key-values pairs
 };
 
 /**
diff --git a/cpp/src/io/avro/reader_impl.cu b/cpp/src/io/avro/reader_impl.cu
index 556ca6b9d80..f39fba0d33b 100644
--- a/cpp/src/io/avro/reader_impl.cu
+++ b/cpp/src/io/avro/reader_impl.cu
@@ -574,7 +574,8 @@ table_with_metadata read_avro(std::unique_ptr<cudf::io::datasource>&& source,
     metadata_out.column_names[i] = selected_columns[i].second;
   }
   // Return user metadata
-  metadata_out.user_data = meta.user_data;
+  metadata_out.user_data          = meta.user_data;
+  metadata_out.per_file_user_data = {{meta.user_data.begin(), meta.user_data.end()}};
 
   return {std::make_unique<table>(std::move(out_columns)), std::move(metadata_out)};
 }
diff --git a/cpp/src/io/orc/reader_impl.cu b/cpp/src/io/orc/reader_impl.cu
index 139eb28d1a1..f64ba6f0566 100644
--- a/cpp/src/io/orc/reader_impl.cu
+++ b/cpp/src/io/orc/reader_impl.cu
@@ -1262,11 +1262,21 @@ table_with_metadata reader::impl::read(size_type skip_rows,
 
   out_metadata.schema_info = std::move(schema_info);
 
-  for (const auto& meta : _metadata.per_file_metadata) {
-    for (const auto& kv : meta.ff.metadata) {
-      out_metadata.user_data.insert({kv.name, kv.value});
-    }
-  }
+  std::transform(_metadata.per_file_metadata.cbegin(),
+                 _metadata.per_file_metadata.cend(),
+                 std::back_inserter(out_metadata.per_file_user_data),
+                 [](auto& meta) {
+                   std::unordered_map<std::string, std::string> kv_map;
+                   std::transform(meta.ff.metadata.cbegin(),
+                                  meta.ff.metadata.cend(),
+                                  std::inserter(kv_map, kv_map.end()),
+                                  [](auto const& kv) {
+                                    return std::pair{kv.name, kv.value};
+                                  });
+                   return kv_map;
+                 });
+  out_metadata.user_data = {out_metadata.per_file_user_data[0].begin(),
+                            out_metadata.per_file_user_data[0].end()};
 
   return {std::make_unique<table>(std::move(out_columns)), std::move(out_metadata)};
 }
diff --git a/cpp/src/io/parquet/reader_impl.cu b/cpp/src/io/parquet/reader_impl.cu
index f165bd5ec3b..c3537833908 100644
--- a/cpp/src/io/parquet/reader_impl.cu
+++ b/cpp/src/io/parquet/reader_impl.cu
@@ -317,10 +317,10 @@ struct metadata : public FileMetaData {
 };
 
 class aggregate_reader_metadata {
-  std::vector<metadata> const per_file_metadata;
-  std::map<std::string, std::string> const agg_keyval_map;
-  size_type const num_rows;
-  size_type const num_row_groups;
+  std::vector<metadata> per_file_metadata;
+  std::vector<std::unordered_map<std::string, std::string>> keyval_maps;
+  size_type num_rows;
+  size_type num_row_groups;
   /**
    * @brief Create a metadata object from each element in the source vector
    */
@@ -335,18 +335,26 @@ class aggregate_reader_metadata {
   }
 
   /**
-   * @brief Merge the keyvalue maps from each per-file metadata object into a single map.
+   * @brief Collect the keyvalue maps from each per-file metadata object into a vector of maps.
    */
-  auto merge_keyval_metadata()
+  [[nodiscard]] auto collect_keyval_metadata()
   {
-    std::map<std::string, std::string> merged;
-    // merge key/value maps TODO: warn/throw if there are mismatches?
-    for (auto const& pfm : per_file_metadata) {
-      for (auto const& kv : pfm.key_value_metadata) {
-        merged[kv.key] = kv.value;
-      }
-    }
-    return merged;
+    std::vector<std::unordered_map<std::string, std::string>> kv_maps;
+    std::transform(per_file_metadata.cbegin(),
+                   per_file_metadata.cend(),
+                   std::back_inserter(kv_maps),
+                   [](auto const& pfm) {
+                     std::unordered_map<std::string, std::string> kv_map;
+                     std::transform(pfm.key_value_metadata.cbegin(),
+                                    pfm.key_value_metadata.cend(),
+                                    std::inserter(kv_map, kv_map.end()),
+                                    [](auto const& kv) {
+                                      return std::pair{kv.key, kv.value};
+                                    });
+                     return kv_map;
+                   });
+
+    return kv_maps;
   }
 
   /**
@@ -374,7 +382,7 @@ class aggregate_reader_metadata {
  public:
   aggregate_reader_metadata(std::vector<std::unique_ptr<datasource>> const& sources)
     : per_file_metadata(metadatas_from_sources(sources)),
-      agg_keyval_map(merge_keyval_metadata()),
+      keyval_maps(collect_keyval_metadata()),
       num_rows(calc_num_rows()),
       num_row_groups(calc_num_row_groups())
   {
@@ -425,7 +433,7 @@ class aggregate_reader_metadata {
     return per_file_metadata[0].schema[schema_idx];
   }
 
-  [[nodiscard]] auto const& get_key_value_metadata() const { return agg_keyval_map; }
+  [[nodiscard]] auto const& get_key_value_metadata() const { return keyval_maps; }
 
   /**
    * @brief Gets the concrete nesting depth of output cudf columns
@@ -461,8 +469,10 @@ class aggregate_reader_metadata {
    */
   [[nodiscard]] std::string get_pandas_index() const
   {
-    auto it = agg_keyval_map.find("pandas");
-    if (it != agg_keyval_map.end()) {
+    // Assumes that all input files have the same metadata
+    // TODO: verify this assumption
+    auto it = keyval_maps[0].find("pandas");
+    if (it != keyval_maps[0].end()) {
       // Captures a list of quoted strings found inside square brackets after `"index_columns":`
       // Inside quotes supports newlines, brackets, escaped quotes, etc.
       // One-liner regex:
@@ -1759,7 +1769,9 @@ table_with_metadata reader::impl::read(size_type skip_rows,
   }
 
   // Return user metadata
-  out_metadata.user_data = _metadata->get_key_value_metadata();
+  out_metadata.per_file_user_data = _metadata->get_key_value_metadata();
+  out_metadata.user_data          = {out_metadata.per_file_user_data[0].begin(),
+                            out_metadata.per_file_user_data[0].end()};
 
   return {std::make_unique<table>(std::move(out_columns)), std::move(out_metadata)};
 }