Around 350 engineers will join colleagues working at Great Western Railways (GWR) as well as across the network and strike on 1 October over salaries.
The union Unite said that, despite a current inflation rate of 9.9 per cent, GWR engineers were not offered a pay increase.
Disruption will affect the operator’s depots and stations around England – including London, Exeter and Oxford.
“Any disruption to Great Western Railways’ services will be entirely the fault of the company for failing to put forward a pay rise,” said Unite’s regional officer John McGookin.
“They must come back with an acceptable offer.”
Rail Delivery Group’s director of industry operations Daniel Mann called the walkout “unnecessary and damaging.”
More than 40,000 members of the union RMT working at Network Rail and 14 other operators – including GWR – will walk out on Saturday in a long-standing dispute over security, pay and conditions.
The 24-hour strike will fall on the same day as the strike announced by the train drivers’ union Aslef.
The industrial action was initially postponed following the Queen’s death but was put back on last week.