diff --git a/IMPLEMENTATION_COVERAGE.md b/IMPLEMENTATION_COVERAGE.md
index d8e02f59..d6a4d817 100644
--- a/IMPLEMENTATION_COVERAGE.md
+++ b/IMPLEMENTATION_COVERAGE.md
@@ -4766,7 +4766,7 @@
 - [X] list_targets_for_policy
 - [X] move_account
 - [ ] remove_account_from_organization
-- [ ] tag_resource
+- [x] tag_resource
 - [ ] untag_resource
 - [ ] update_organizational_unit
 - [ ] update_policy
diff --git a/moto/organizations/models.py b/moto/organizations/models.py
index d558616d..2fb0a665 100644
--- a/moto/organizations/models.py
+++ b/moto/organizations/models.py
@@ -57,6 +57,7 @@ class FakeAccount(BaseModel):
         self.joined_method = "CREATED"
         self.parent_id = organization.root_id
         self.attached_policies = []
+        self.tags = {}
 
     @property
     def arn(self):
@@ -442,5 +443,17 @@ class OrganizationsBackend(BaseBackend):
         ]
         return dict(Targets=objects)
 
+    def tag_resource(self, **kwargs):
+        account = next((a for a in self.accounts if a.id == kwargs["ResourceId"]), None)
+
+        if account is None:
+            raise RESTError(
+                "InvalidInputException",
+                "You provided a value that does not match the required pattern.",
+            )
+
+        new_tags = {tag["Key"]: tag["Value"] for tag in kwargs["Tags"]}
+        account.tags.update(new_tags)
+
 
 organizations_backend = OrganizationsBackend()
diff --git a/moto/organizations/responses.py b/moto/organizations/responses.py
index f9e0b2e0..11093bae 100644
--- a/moto/organizations/responses.py
+++ b/moto/organizations/responses.py
@@ -119,3 +119,8 @@ class OrganizationsResponse(BaseResponse):
         return json.dumps(
             self.organizations_backend.list_targets_for_policy(**self.request_params)
         )
+
+    def tag_resource(self):
+        return json.dumps(
+            self.organizations_backend.tag_resource(**self.request_params)
+        )
diff --git a/tests/test_organizations/test_organizations_boto3.py b/tests/test_organizations/test_organizations_boto3.py
index 3b4a5155..95b11554 100644
--- a/tests/test_organizations/test_organizations_boto3.py
+++ b/tests/test_organizations/test_organizations_boto3.py
@@ -3,6 +3,7 @@ from __future__ import unicode_literals
 import boto3
 import json
 import six
+import sure  # noqa
 from botocore.exceptions import ClientError
 from nose.tools import assert_raises
 
@@ -605,3 +606,32 @@ def test_list_targets_for_policy_exception():
     ex.operation_name.should.equal("ListTargetsForPolicy")
     ex.response["Error"]["Code"].should.equal("400")
     ex.response["Error"]["Message"].should.contain("InvalidInputException")
+
+
+@mock_organizations
+def test_tag_resource():
+    client = boto3.client("organizations", region_name="us-east-1")
+    client.create_organization(FeatureSet="ALL")
+    account_id = client.create_account(AccountName=mockname, Email=mockemail)[
+        "CreateAccountStatus"
+    ]["AccountId"]
+
+    client.tag_resource(ResourceId=account_id, Tags=[{"Key": "key", "Value": "value"}])
+
+
+@mock_organizations
+def test_tag_resource_errors():
+    client = boto3.client("organizations", region_name="us-east-1")
+    client.create_organization(FeatureSet="ALL")
+
+    with assert_raises(ClientError) as e:
+        client.tag_resource(
+            ResourceId="000000000000", Tags=[{"Key": "key", "Value": "value"},]
+        )
+    ex = e.exception
+    ex.operation_name.should.equal("TagResource")
+    ex.response["Error"]["Code"].should.equal("400")
+    ex.response["Error"]["Message"].should.contain("InvalidInputException")
+    ex.response["Error"]["Message"].should.contain(
+        "You provided a value that does not match the required pattern."
+    )