Mon Motors, the AM100 car dealer with showrooms across Wales and South West England, boosted pre-tax profits by 24% in 2014.
The dealer group, with 10 showrooms selling Audi, Volkswagen, Ford, Skoda and Seat cars as well as Ford LCVs, has published 2014 accounts showing pre-tax profits rose to £3.1m from £2.5m, and turnover grew to £294.3m from £258.3m.
The average number of staff employed by the business also increased to 657 from 626.
In their accounts filed with Companies House, the directors said: "There was a surge on car registrations in October 2014, which ensured that the increase in car registrations over 2013 was maintained for the year.
"The overall increase for the year was 9.35% on 2013 with all the franchises increasing their sales. The overall market share of the five brands that are represented remained consistent with 2013.
"The results for the year and the financial position at the year end were considered satisfactory by the directors, who are confident 2015 will see the company continue being profitable."
They added that the company's investment in its Merthyr Tydfil dealership, which was extended in 2013, had led to a good year, but its Bath VW showroom was completed later than planned which caused "major disruption".
But they said that all its dealership properties are now up to date and there was "continued investment in corporate identity".
The company is one of the largest in the area by turnover and has recently been named as one of the fastest growing in the UK by BDO and the Sunday Times.