diff --git a/docs/metadata-workflow.rst b/docs/metadata-workflow.rst
--- a/docs/metadata-workflow.rst
+++ b/docs/metadata-workflow.rst
@@ -166,7 +166,7 @@
 (other than the `codemeta` mapping, which is the identity function, and
 therefore supports all properties):
 
-.. program-output:: python3 -m swh.indexer.cli mapping list-terms --exclude-mapping codemeta --exclude-mapping sword-codemeta
+.. program-output:: python3 -m swh.indexer.cli mapping list-terms --exclude-mapping codemeta --exclude-mapping json-sword-codemeta --exclude-mapping sword-codemeta
     :nostderr:
 
 
diff --git a/swh/indexer/metadata_dictionary/__init__.py b/swh/indexer/metadata_dictionary/__init__.py
--- a/swh/indexer/metadata_dictionary/__init__.py
+++ b/swh/indexer/metadata_dictionary/__init__.py
@@ -25,6 +25,7 @@
 
 EXTRINSIC_MAPPINGS: Dict[str, Type[BaseExtrinsicMapping]] = {
     "GitHubMapping": github.GitHubMapping,
+    "JsonSwordCodemetaMapping": codemeta.JsonSwordCodemetaMapping,
     "SwordCodemetaMapping": codemeta.SwordCodemetaMapping,
 }
 
diff --git a/swh/indexer/metadata_dictionary/codemeta.py b/swh/indexer/metadata_dictionary/codemeta.py
--- a/swh/indexer/metadata_dictionary/codemeta.py
+++ b/swh/indexer/metadata_dictionary/codemeta.py
@@ -9,6 +9,8 @@
 from typing import Any, Dict, List, Optional, Tuple
 import xml.etree.ElementTree as ET
 
+import xmltodict
+
 from swh.indexer.codemeta import CODEMETA_CONTEXT_URL, CODEMETA_TERMS, compact, expand
 
 from .base import BaseExtrinsicMapping, SingleFileIntrinsicMapping
@@ -115,3 +117,33 @@
 
     def normalize_translation(self, metadata: Dict[str, Any]) -> Dict[str, Any]:
         return compact(metadata, forgefed=False)
+
+
+class JsonSwordCodemetaMapping(SwordCodemetaMapping):
+    """
+    Variant of :class:`SwordCodemetaMapping` that reads the legacy
+    ``sword-v2-atom-codemeta-v2-in-json`` format and converts it back to
+    ``sword-v2-atom-codemeta-v2`` XML
+    """
+
+    name = "json-sword-codemeta"
+
+    @classmethod
+    def extrinsic_metadata_formats(cls) -> Tuple[str, ...]:
+        return ("sword-v2-atom-codemeta-v2-in-json",)
+
+    def translate(self, content: bytes) -> Optional[Dict[str, Any]]:
+        # ``content`` was generated by calling ``xmltodict.parse()`` on a XML document,
+        # so ``xmltodict.unparse()`` is guaranteed to return a document that is
+        # semantically equivalent to the original and pass it to SwordCodemetaMapping.
+        json_doc = json.loads(content)
+
+        if json_doc.get("@xmlns") != ATOM_URI:
+            # Technically, non-default XMLNS were allowed, but it does not seem like
+            # anyone used them, so they do not need to be implemented here.
+            raise NotImplementedError(f"Unexpected XMLNS set: {json_doc}")
+
+        # Root tag was stripped by swh-deposit
+        json_doc = {"entry": json_doc}
+
+        return super().translate(xmltodict.unparse(json_doc))
diff --git a/swh/indexer/tests/metadata_dictionary/test_codemeta.py b/swh/indexer/tests/metadata_dictionary/test_codemeta.py
--- a/swh/indexer/tests/metadata_dictionary/test_codemeta.py
+++ b/swh/indexer/tests/metadata_dictionary/test_codemeta.py
@@ -349,3 +349,19 @@
             "Codemeta Name 2",
         ],
     }
+
+
+def test_json_sword():
+    content = """{"id": "hal-01243573", "@xmlns": "http://www.w3.org/2005/Atom", "author": {"name": "Author 1", "email": "foo@example.org"}, "client": "hal", "codemeta:url": "http://example.org/", "codemeta:name": "The assignment problem", "@xmlns:codemeta": "https://doi.org/10.5063/SCHEMA/CODEMETA-2.0", "codemeta:author": {"codemeta:name": "Author 2"}, "codemeta:license": {"codemeta:name": "GNU General Public License v3.0 or later"}}"""  # noqa
+    result = MAPPINGS["JsonSwordCodemetaMapping"]().translate(content)
+    assert result == {
+        "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
+        "author": [
+            {"name": "Author 1", "email": "foo@example.org"},
+            {"name": "Author 2"},
+        ],
+        "license": {"name": "GNU General Public License v3.0 or later"},
+        "name": "The assignment problem",
+        "schema:url": "http://example.org/",
+        "name": "The assignment problem",
+    }
diff --git a/swh/indexer/tests/test_cli.py b/swh/indexer/tests/test_cli.py
--- a/swh/indexer/tests/test_cli.py
+++ b/swh/indexer/tests/test_cli.py
@@ -111,6 +111,7 @@
             "composer",
             "gemspec",
             "github",
+            "json-sword-codemeta",
             "maven",
             "npm",
             "nuget",
@@ -150,6 +151,8 @@
             "--exclude-mapping",
             "codemeta",
             "--exclude-mapping",
+            "json-sword-codemeta",
+            "--exclude-mapping",
             "sword-codemeta",
         ],
         catch_exceptions=False,