diff --git a/docs/source/pages/protocols/uws.rst b/docs/source/pages/protocols/uws.rst
index 27c30f8..d9d346c 100644
--- a/docs/source/pages/protocols/uws.rst
+++ b/docs/source/pages/protocols/uws.rst
@@ -59,6 +59,9 @@ Represents a single parameter of a UWS job.
             :start-after: parameter-xml-start
             :end-before: parameter-xml-end
 
+For multi-valued attributes, use the type `vo_models.uws.models.MultiValuedParameter` instead of ``list[Parameter]``.
+This is equivalent to ``list[Parameter]`` but adds some special validation support required for multi-valued UWS job parameters.
+
 Parameters
 **********
 
@@ -225,4 +228,4 @@ The following simple types are provided in the ``vo_models.uws`` package for use
 
 - :py:class:`vo_models.uws.types.ErrorType`
 - :py:class:`vo_models.uws.types.ExecutionPhase`
-- :py:class:`vo_models.uws.types.UWSVersion`
\ No newline at end of file
+- :py:class:`vo_models.uws.types.UWSVersion`
diff --git a/pyproject.toml b/pyproject.toml
index ceee6a9..b9bbae1 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -14,6 +14,7 @@ readme = "README.md"
 requires-python = ">=3.10"
 
 dependencies = [
+    "pydantic>2",
     "pydantic-xml[lxml]>=2.6.0",
     ]
 
diff --git a/tests/uws/uws_models_test.py b/tests/uws/uws_models_test.py
index d007cca..52803e8 100644
--- a/tests/uws/uws_models_test.py
+++ b/tests/uws/uws_models_test.py
@@ -12,6 +12,7 @@
     ErrorSummary,
     Jobs,
     JobSummary,
+    MultiValuedParameter,
     Parameter,
     Parameters,
     ResultReference,
@@ -257,13 +258,28 @@ class TestParameters(Parameters):
 
         param1: Optional[Parameter] = element(tag="parameter", default=None)
         param2: Optional[Parameter] = element(tag="parameter", default=None)
-        param3: Optional[Parameter] = element(tag="parameter", default=None)
+        param3: Optional[MultiValuedParameter] = element(tag="parameter", default=None)
+        param4: Optional[MultiValuedParameter] = element(tag="parameter", default=None)
+        param5: MultiValuedParameter = element(tag="parameter")
 
     test_parameters_xml = (
         f"<uws:parameters {UWS_NAMESPACE_HEADER}>"
         '<uws:parameter byReference="false" isPost="false" id="param1">value1</uws:parameter>'
         '<uws:parameter byReference="false" isPost="false" id="param2">value2</uws:parameter>'
-        '<uws:parameter byReference="false" isPost="false" id="param3">value3</uws:parameter>'
+        '<uws:parameter byReference="false" isPost="false" id="param4">value4</uws:parameter>'
+        '<uws:parameter byReference="false" isPost="false" id="param4">second value4</uws:parameter>'
+        '<uws:parameter byReference="false" isPost="false" id="param5">value5</uws:parameter>'
+        "</uws:parameters>"
+    )
+
+    # Test that the same parameters are parsed correctly when given out of order.
+    test_parameters_xml_reordered = (
+        f"<uws:parameters {UWS_NAMESPACE_HEADER}>"
+        '<uws:parameter byReference="false" isPost="false" id="param5">value5</uws:parameter>'
+        '<uws:parameter byReference="false" isPost="false" id="param4">value4</uws:parameter>'
+        '<uws:parameter byReference="false" isPost="false" id="param1">value1</uws:parameter>'
+        '<uws:parameter byReference="false" isPost="false" id="param4">second value4</uws:parameter>'
+        '<uws:parameter byReference="false" isPost="false" id="param2">value2</uws:parameter>'
         "</uws:parameters>"
     )
 
@@ -271,15 +287,32 @@ def test_read_from_xml(self):
         """Test reading from XML"""
 
         parameters = self.TestParameters.from_xml(self.test_parameters_xml)
-        self.assertEqual(len(parameters.model_dump()), 3)
+
+        self.assertEqual(len(parameters.dict()), 5)
+
+        self.assertEqual(parameters.param3, None)
+        self.assertEqual(len(parameters.param4), 2)
+        self.assertEqual(len(parameters.param5), 1)
 
         self.assertEqual(parameters.param1.id, "param1")
         self.assertEqual(parameters.param2.id, "param2")
-        self.assertEqual(parameters.param3.id, "param3")
+        self.assertEqual(parameters.param4[0].id, "param4")
+        self.assertEqual(parameters.param4[1].id, "param4")
+        self.assertEqual(parameters.param5[0].id, "param5")
 
         self.assertEqual(parameters.param1.value, "value1")
         self.assertEqual(parameters.param2.value, "value2")
-        self.assertEqual(parameters.param3.value, "value3")
+        self.assertEqual(parameters.param4[0].value, "value4")
+        self.assertEqual(parameters.param4[1].value, "second value4")
+        self.assertEqual(parameters.param5[0].value, "value5")
+
+    def test_read_from_xml_reordered(self):
+        """Test reading from XML out of order"""
+
+        parameters = self.TestParameters.from_xml(self.test_parameters_xml)
+        parameters_reordered = self.TestParameters.from_xml(self.test_parameters_xml_reordered)
+
+        assert parameters == parameters_reordered
 
     def test_write_to_xml(self):
         """Test writing to XML"""
@@ -287,7 +320,12 @@ def test_write_to_xml(self):
         parameters_element = self.TestParameters(
             param1=Parameter(id="param1", value="value1"),
             param2=Parameter(id="param2", value="value2"),
-            param3=Parameter(id="param3", value="value3"),
+            param3=None,
+            param4=[
+                Parameter(id="param4", value="value4"),
+                Parameter(id="param4", value="second value4"),
+            ],
+            param5=[Parameter(id="param5", value="value5")],
         )
         parameters_xml = parameters_element.to_xml(skip_empty=True, encoding=str)
 
@@ -302,7 +340,11 @@ def test_validate(self):
         parameters = self.TestParameters(
             param1=Parameter(id="param1", value="value1"),
             param2=Parameter(id="param2", value="value2"),
-            param3=Parameter(id="param3", value="value3"),
+            param4=[
+                Parameter(id="param4", value="value4"),
+                Parameter(id="param4", value="second value4"),
+            ],
+            param5=[Parameter(id="param5", value="value5")],
         )
         parameters_xml = etree.fromstring(
             parameters.to_xml(skip_empty=True, encoding=str)
diff --git a/vo_models/uws/__init__.py b/vo_models/uws/__init__.py
index 9f19708..7c5f411 100644
--- a/vo_models/uws/__init__.py
+++ b/vo_models/uws/__init__.py
@@ -9,6 +9,7 @@
     Job,
     Jobs,
     JobSummary,
+    MultiValuedParameter,
     Parameter,
     Parameters,
     ParametersType,
diff --git a/vo_models/uws/models.py b/vo_models/uws/models.py
index 4a8b992..21e2368 100644
--- a/vo_models/uws/models.py
+++ b/vo_models/uws/models.py
@@ -1,7 +1,10 @@
 """UWS Job Schema using Pydantic-XML models"""
-from typing import Dict, Generic, Optional, TypeVar
+from typing import Annotated, Dict, Generic, Optional, TypeAlias, TypeVar
 
+
+from pydantic import BeforeValidator
 from pydantic import ConfigDict
+
 from pydantic_xml import BaseXmlModel, attr, element
 
 from vo_models.uws.types import ErrorType, ExecutionPhase, UWSVersion
@@ -42,23 +45,61 @@ class Parameter(BaseXmlModel, tag="parameter", ns="uws", nsmap=NSMAP):
     is_post: Optional[bool] = attr(name="isPost", default=False)
 
 
+MultiValuedParameter: TypeAlias = Annotated[
+    list[Parameter],
+    BeforeValidator(lambda v: v if isinstance(v, list) else [v])
+]
+"""Type for a multi-valued parameter.
+
+This type must be used instead of ``list[Parameter]`` for parameters that may
+take multiple values. The resulting model attribute will be a list of
+`Parameter` objects with the same ``id``.
+"""
+
+
 class Parameters(BaseXmlModel, tag="parameters", ns="uws", nsmap=NSMAP):
-    """
-    An abstract holder of UWS parameters.
+    """An abstract holder of UWS parameters.
 
-    The list of input parameters to the job - if the job description language does not naturally have
-    parameters, then this list should contain one element which is the content of the original POST that created the
-    job.
+    The input parameters to the job. For simple key/value pair parameters, there must be one model field per key, with
+    a type of either `Parameter` or `MultiValuedParameter` depending on whether it can be repeated. If the job
+    description language does not naturally have parameters, then this model should contain one element, which is the
+    content of the original POST that created the job.
     """
 
     def __init__(__pydantic_self__, **data) -> None:  # pylint: disable=no-self-argument
-        # during init -- especially if reading from xml -- we may not get the parameters in the order
-        # pydantic-xml expects. This will remap the dict with keys based on the parameter id.
-        parameter_vals = [val for val in data.values() if val is not None]
+        # pydantic-xml's from_xml method only knows how to gather parameters by tag, not by attribute, but UWS job
+        # parameters all use the same tag and distinguish between different parameters by the id attribute. Therefore,
+        # the input data that we get from pydantic-xml will have assigned the Parameter objects to the model attributes
+        # in model declaration order. This may be wildly incorrect if the input parameters were specified in a
+        # different order than the model.
+        #
+        # This processing collapses all of the parameters down to a simple list, turns that into a dict to Parameter
+        # objects or lists of Parameter objects by id attribute values, and then calls the parent constructor with that
+        # as the input data instead. This should cause Pydantic to associate the job parameters with the correct model
+        # attributes.
+        parameter_vals = []
+        for val in data.values():
+            if val is None:
+                continue
+            elif isinstance(val, list):
+                parameter_vals.extend(v for v in val if v is not None)
+            else:
+                parameter_vals.append(val)
+
+        # Reconstruct the proper input parameters to the model based on the id attribute of the parameters. First
+        # convert each parameter to a Parameter object, and then turn the parameters into a dict mapping the id to a
+        # value or list of values. If we see multiple parameters with the same id, assume the parameter may be
+        # multivalued and build a list. If this assumption is incorrect, Pydantic will reject the list during input
+        # validation.
         remapped_vals = {}
         for param in parameter_vals:
             if isinstance(param, dict):
-                remapped_vals[param["id"]] = Parameter(**param)
+                param = Parameter(**param)
+            if param.id in remapped_vals:
+                if isinstance(remapped_vals[param.id], list):
+                    remapped_vals[param.id].append(param)
+                else:
+                    remapped_vals[param.id] = [remapped_vals[param.id], param]
             else:
                 remapped_vals[param.id] = param
         data = remapped_vals