Accounts for the family-owned firm filed at Companies House show Dingbro made a pre-tax profit of £1 million in the year to September compared with £5 million the preceding year.
Turnover increased by 3 per cent, to £131.8 million from £128.1 million.
Director James Dingwall wrote in the accounts: "The automotive market is not immune to market pressures which has led to an extremely competitive market and we have had to respond to that competitiveness. Our focus remains on building a business of significant scale and quality.
"Our results in the accounts reflect our long- term approach to the business as we continue to invest in branches, information technology and systems."
The Aberdeen-based business opened branches in Galashiels and East Kilbride during the year. It has 28 branches across Scotland.
The average number of people employed by Dingbro increased to 1,270 during the year to September from 1,210 in the preceding year.
Mr Dingwall said Dingbro is on track to increase profits in the current year, which has three months to run.