Planning on travelling overseas, like to Europe or Australia, with your Mastercard or Visa Debit Card?

The answer is yes, it will work as a signature transaction the same way that a credit card is accepted. I've never had a problem using my US-issued Paypal Debit MasterCard or US-issued National City Debit Visa Card in Canada. I don't see why I'd have a problem overseas either. 

Doing cash withdrawls at an ATM may be subject to extra fees. There usually will be a currency conversion charge or some such, but it isn't too major. 

If travelling overseas, be sure to keep a copy of the Visa International Customer Service Numbers and/or the Mastercard International Customer Service Numbers.