diff --git a/lib/basecrm/services/contacts_service.rb b/lib/basecrm/services/contacts_service.rb
index 19e1556..d199519 100644
--- a/lib/basecrm/services/contacts_service.rb
+++ b/lib/basecrm/services/contacts_service.rb
@@ -103,6 +103,28 @@ def update(contact)
       Contact.new(root[:data])
     end
 
+    # Upsert a contact
+    #
+    # post '/contacts/upsert?filter_param=filter_value 
+    #
+    # Create a new contact or update an existing, based on a value of a filter or a set of filters. 
+    # At least a single filter - query parameter - is required. If no parameters are present, the request will return an error.
+    # See full docs https://developers.getbase.com/docs/rest/reference/contacts
+    #
+    # @param filters [Hash] - hash contain filters, one level deep e.g. { name: 'string', 'custom_fields[field]': 'value' }
+    # @param contact [Contact, Hash] - This object's attributes describe the object to be updated or created
+    # @return [Contact] The resulting object representing updated or created resource.
+    def upsert(filters, contact)
+      validate_upsert_filters!(filters)
+      validate_type!(contact)
+
+      attributes = sanitize(contact)
+      query_string = URI.encode_www_form(filters)
+      _, _, root = @client.post("/contacts/upsert?#{query_string}", attributes)
+
+      Contact.new(root[:data])
+    end
+
 
     # Delete a contact
     #
@@ -125,6 +147,11 @@ def validate_type!(contact)
       raise TypeError unless contact.is_a?(Contact) || contact.is_a?(Hash)
     end
 
+    def validate_upsert_filters!(filters)
+      raise TypeError unless filters.is_a?(Hash)
+      raise ArgumentError, "at least one filter is required" if filters.empty?
+    end
+
     def extract_params!(contact, *args)
       params = contact.to_h.select{ |k, _| args.include?(k) }
       raise ArgumentError, "one of required attributes is missing. Expected: #{args.join(',')}" if params.count != args.length
diff --git a/lib/basecrm/services/deals_service.rb b/lib/basecrm/services/deals_service.rb
index 581bd20..d062ff8 100644
--- a/lib/basecrm/services/deals_service.rb
+++ b/lib/basecrm/services/deals_service.rb
@@ -105,6 +105,28 @@ def update(deal)
       Deal.new(root[:data])
     end
 
+    # Upsert a deal
+    #
+    # post '/deals/upsert?filter_param=filter_value 
+    #
+    # Create a new deal or update an existing, based on a value of a filter or a set of filters. 
+    # At least a single filter - query parameter - is required. If no parameters are present, the request will return an error.
+    # See full docs https://developers.getbase.com/docs/rest/reference/deals
+    #
+    # @param filters [Hash] - hash contain filters, one level deep e.g. { name: 'string', 'custom_fields[field]': 'value' }
+    # @param deal [Deal, Hash] - This object's attributes describe the object to be updated or created
+    # @return [Deal] The resulting object representing updated or created resource.
+    def upsert(filters, deal)
+      validate_upsert_filters!(filters)
+      validate_type!(deal)
+
+      attributes = sanitize(deal)
+      query_string = URI.encode_www_form(filters)
+      _, _, root = @client.post("/deals/upsert?#{query_string}", attributes)
+
+      Deal.new(root[:data])
+    end
+
 
     # Delete a deal
     #
@@ -127,6 +149,11 @@ def validate_type!(deal)
       raise TypeError unless deal.is_a?(Deal) || deal.is_a?(Hash)
     end
 
+    def validate_upsert_filters!(filters)
+      raise TypeError unless filters.is_a?(Hash)
+      raise ArgumentError, "at least one filter is required" if filters.empty?
+    end
+
     def extract_params!(deal, *args)
       params = deal.to_h.select{ |k, _| args.include?(k) }
       raise ArgumentError, "one of required attributes is missing. Expected: #{args.join(',')}" if params.count != args.length
diff --git a/spec/services/contacts_service_spec.rb b/spec/services/contacts_service_spec.rb
index 46b81ce..a3532fb 100644
--- a/spec/services/contacts_service_spec.rb
+++ b/spec/services/contacts_service_spec.rb
@@ -9,6 +9,7 @@
     it { should respond_to :destroy }
     it { should respond_to :find }
     it { should respond_to :update }
+    it { should respond_to :upsert }
     it { should respond_to :where }
   end
 
@@ -48,6 +49,22 @@
     end
   end
 
+  describe :upsert do
+    it 'raises a TypeError if filters is nil' do
+      expect(client.contacts.upsert(nil, { name: 'unique_name' }).to raise_error(TypeError)
+    end
+
+    it 'raises an ArgumentError if filters is empty' do
+      expect(client.contacts.upsert({}, { name: 'unique_name' }).to raise_error(ArgumentError)
+    end
+
+    it 'calls the upsert route with encoded filters' do
+      filters = { last_name: 'unique_name', 'custom_fields[external_id]': 'unique-1' }
+      contact = create(:contact, last_name: 'unique_name', custom_fields: { external_id: 'unique-1'})
+      expect(client.contacts.upsert(filters, contact)).to be_instance_of BaseCRM::Contact
+    end
+  end
+
   describe :destroy do
     it "returns true on success" do
       @contact = create(:contact)
diff --git a/spec/services/deals_service_spec.rb b/spec/services/deals_service_spec.rb
index 8f5b0c6..a8e187d 100644
--- a/spec/services/deals_service_spec.rb
+++ b/spec/services/deals_service_spec.rb
@@ -9,6 +9,7 @@
     it { should respond_to :destroy }
     it { should respond_to :find }
     it { should respond_to :update }
+    it { should respond_to :upsert }
     it { should respond_to :where }
 
   end
@@ -59,6 +60,22 @@
     end
   end
 
+  describe :upsert do
+    it 'raises a TypeError if filters is nil' do
+      expect(client.deals.upsert(nil, { name: 'unique_name' }).to raise_error(TypeError)
+    end
+
+    it 'raises an ArgumentError if filters is empty' do
+      expect(client.deals.upsert({}, { name: 'unique_name' }).to raise_error(ArgumentError)
+    end
+
+    it 'calls the upsert route with encoded filters' do
+      filters = { name: 'unique_name', 'custom_fields[external_id]': 'unique-1' }
+      deal = create(:deal, name: 'unique_name', custom_fields: { external_id: 'unique-1'})
+      expect(client.deals.upsert(filters, deal)).to be_instance_of BaseCRM::Deal
+    end
+  end
+ 
   describe :destroy do
     it "returns true on success" do
       @deal = create(:deal)