Goals from Marvin Williams, Charlie MacDonald and Nathan Elder saw off Havant and Waterlooville 3-1 in Sunday's televised FA Cup tie.
But it needed some fine reflex saves from Ben Hamer to ensure Brentford's safe passage to a second round tie away to Barrow or Eastbourne.
Hamer came to the rescue soon after Ian Simpemba had headed the Blue Square South Conference side back into contention at 2-1, blocking three shots on the line.
The game was mostly scrappy, but Bees boss andy Scott was delighted his team did a professional job to see off last season's cup giant-killers.
"We knew it was going to be a messy game," Scott said. "It wasn't pretty but it didn't need to be. We got the job done."