diff --git a/tildes/requirements-dev.txt b/tildes/requirements-dev.txt
index 1634bef..00235ab 100644
--- a/tildes/requirements-dev.txt
+++ b/tildes/requirements-dev.txt
@@ -37,7 +37,7 @@ jinja2==3.1.6
 lupa==2.5
 mako==1.3.10
 markupsafe==3.0.2
-marshmallow==3.25.1
+marshmallow==4.0.1
 matplotlib-inline==0.1.7
 mccabe==0.7.0
 mypy==1.17.1
diff --git a/tildes/requirements.in b/tildes/requirements.in
index a7ee0cf..5a05438 100644
--- a/tildes/requirements.in
+++ b/tildes/requirements.in
@@ -10,7 +10,7 @@ html5lib
 invoke
 ipython
 lupa
-marshmallow==3.25.1 # TODO: Upgrade Marshmallow https://marshmallow.readthedocs.io/en/latest/upgrading.html
+marshmallow
 Pillow
 pip-tools
 prometheus-client
diff --git a/tildes/requirements.txt b/tildes/requirements.txt
index 477544c..a9c2ef4 100644
--- a/tildes/requirements.txt
+++ b/tildes/requirements.txt
@@ -25,7 +25,7 @@ jinja2==3.1.6
 lupa==2.5
 mako==1.3.10
 markupsafe==3.0.2
-marshmallow==3.25.1
+marshmallow==4.0.1
 matplotlib-inline==0.1.7
 packaging==25.0
 parso==0.8.4