The local government district of Brentford, the civil parishes of Heston, Isleworth, Norwood, and Twickenham, and part of the civil parish of Hanwell.
The constituency was located in the south-west of the historic county of Middlesex, in what is now West London. It was a division of the county, named after the town of Brentford, on the north (or Middlesex) bank of the River Thames.
The seat was surrounded by the constituencies of Ealing to the north-east, Kingston to the east, Epsom to the south and Uxbridge to the west and north-west.
Another General Election was required to take place before the end of 1915. The political parties had been making preparations for an election to take place and by the July 1914, the following candidates had been selected;