The issue of shorter trains was raised in the Commons by a local MP
Southeastern trains is reinstating carriages on some peak services after commuters complained of overcrowding.
The firm, which serves Kent and parts of East Sussex, Surrey and London, had shortened off-peak and peak trains after reviewing passenger numbers.
But it said some peak services were being restored after passengers complained about a lack of seats.
Greg Clark, Tunbridge Wells Tory MP, who raised the issue in the Commons, called it a "victory for common sense".
A spokeswoman for Southeastern said a few peak trains were being made longer again after feedback from commuters who had found they were "less likely" to get a seat.
She said the company had received complaints about crowding which had been taken into consideration.
RAIL SERVICES TO BE RESTORED
0720 Tunbridge Wells to London Charing Cross
0740 Tunbridge Wells to London Charing Cross
1741 London Charing Cross to Tunbridge Wells
1828 London Charing Cross to Tunbridge Wells
0713 Sevenoaks to London Cannon Street
0745 Hayes to London Cannon Street
1656 London Victoria to Ashford via Maidstone East
But she added: "We can't guarantee people getting a seat - that's already the case."
The majority of services would stay at the new length which was "more environmentally-friendly", she said.
She said the company had tried to evaluate how to use its carriages more efficiently and it was "not efficient to run longer trains during the day".
The train operator regularly reviewed its services and monitored passenger numbers, using head counts and load weight software, to assess how many people were on a service, she said.
Train formations were based on the number people using services and economical and environmental reasons.
All carriages - apart from those undergoing maintenance, overhaul or repair - were in use, she added.