The first of 80 new District Line trains have arrived at the Wimbledon to Edgware Road branch.
Commuters to central London will have seen the new look trains on the Circle Line last year, which are air-conditioned and have walk-through carriages, similar to the Docklands Light Railway.
They also have wider doors and walkways, lower passenger alarms and a smaller gap between the train and platform.
All 80 new trains should be in place by 2016, after five extra trains were introduced on the Wimbledon-Edgware Road branch in 2012 when TfL reduced the Olympia-Earls Court service.
The new trains were due to arrive in 2013 and a signalling upgrade should be in place by 2018.
The money for the District Line improvements was pledged in 2002 by Metronet, who told commuters they would have to wait 16 years for improvements to what they admitted was an under-funded tube line.