The hosts had the perfect start with Martin Devaney blasting home from Jose Baxter’s cross in the fourth minute but the Rovers midfielder was cautioned for his celebrations.
Dean had no joy with three headed efforts for Brentford and then Sam Saunders missed the target after a part clearance.
Bees goalkeeper Richard Lee saved well from Mustafa Tiryaki’s 25-yard strike before the visitors levelled after 22 minutes. Gary Alexander hit the target as Tranmere failed to deal with a right-wing cross by Clayton Donaldson.
Brentford went ahead 10 minutes later with Alexander this time turning provider for Donaldson to power a right foot shot out of the reach of keeper Paul Rachubka.
It became 2-2 after 55 minutes with Dean unlucky to deflect a cross by Danny Holmes out of the reach of Lee for an own goal. Dean almost made amends in the 80th minute but his shot was blocked on the line by Ash Taylor.