First Essex was originally part of the Eastern National Omnibus Company, founded in 1929, nationalised in 1949 and privatised in a management buyout in October 1986.

[2] First Essex was criticised by passengers and members of the Southend Area Bus Users' Group for withdrawing services which it considered no longer economically viable when Southend Borough Council withdrew bus subsidies as part of budget cuts in 2005.

They replaced it with a more expensive "Octopus" ticket, issued by and can be used on any buses operated by companies running in the general Southend area.

[5] First Essex operates four bus depots in the cities of Colchester, and Chelmsford, and the towns of Basildon and Hadleigh.

Chelmsford depot operates routes C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C57, 3, 4, 13/A/B, 14, 19/A, X30 Essex Airlink, 31, 37, 42A, 46, 47, 59, 70, X70, 71, X71, 73/A/B, 80A/C, 170, 322, 323, 324, 331, 332, 336, 351, 370, 371, 372, 407, 417 and school bus services 525, 570, 620, 621.

When the old Duke Street bus depot/bus station was demolished in autumn 2004, operations moved to a new site at Westway.

[7] From its opening in 2007 until 2022, it had been the operator of the Chelmsford Park and Ride service; the contract was lost to Vectare.

Colchester operates the following as part of the Essex Bus brand, with services 370, 371 and X71 being shared with Chelmsford Depot.

It was built in 2016 to replace the old garage on Queen Street, which was on the site of the Theatre Royal that burned down circa 1917.

This has since been bought by a local company that is not transport orientated; in 2015, First demolished the old timber yard (its former use) and built a new bus garage.

Service buses still terminate outside and locals still refer to it as West Mersea bus station.

The predecessor of Prittlewell, Southend (SD) depot on London Road, closed in 1987 and has now disappeared under a Sainsbury's store.

Fairfield Road had originally been used by Hicks Brothers, a bus operator which Eastern National took over in 1949.

Clacton depot has been at Telford Road, on the Gorse Lane industrial estate, since 1988 at premises previously occupied by Coastal Red, a one-time competitor on the Tendring peninsular later bought by Eastern National.

The predecessor of Walton garage was Warners Iron Foundry at Naze Park Road, a building stands to this day.

The depot at Harwich Bus Station, off Main Road, was opened by Eastern National in 1974.