 <p>Yes. All SQL Server releases, from 2005 to 2014 inclusive, are <a href="http://rusanu.com/2007/11/28/is-service-broker-in-sql-server-2008-compatible-with-the-one-in-sql-server-2005/" rel="nofollow">compatible with each other at the Service Broker</a> layer. In fact the 2008 instances are not even going to be able to figure out they are talking to 2014.</p> <p>You should be able to migrate one machine at a time, w/o taking down everything. If the upgrades are don in-place (keeping the machine name the same and preserving the SSB endpoint settings) then you won't have to change anything after the upgrade, it should just keep working.</p> <p>If you do side-by-side upgrade then you will have to port the SSB endpoint settings and certificates used from one instance to the other, along with moving the database.</p> <p>Keep in mind that if you have a problem and you are forced to rollback to a backup then your entire, distributed, system state will not be consistent (basically conversations will no longer match the send sequence number and receive sequence numbers) and you may have to force some close conversations (manual END ... WITH CLEANUP on a case by case) or nuke the entire broker in the DB (ALTER DATABASE ... SET NEW_BROKER). Lets hope you won't have to do this. If is feasible then you could simply stop the entire system (eg. run ALTER ENDPOINT ... STATE = STOPPED on all 3 nodes to stop all SSB communication) and then do a backup and then do the upgrade, now being safe to rollback the upgrade and restore since everythign is 'frozen'.</p>