The data from the China Automobile Dealers Association (CADA), which was reported by local media on Monday, also showed that overall sales of imported cars during the first half of 2018 fell 22.1 percent year-on-year to 451,971 vehicles.
CADA published the June data last week and has yet to release July figures.
In May, China announced that it would steeply cut import tariffs for foreign-made automobiles and car parts to 15 percent from 25 percent from July 1.
It, however, in July raised tariffs on cars imported from the United States to 40 percent amid rising trade tensions with Washington.
"June was the most impacted month," said Wang Cun, director of the China Automobile Dealers Association's import committee.
"Many car dealers held back their import orders and decided not to import until July 1," he said.
China imported 1.25 million cars last year, according to data from the China Association of Automobile Manufacturers.
The tariff cuts announced in May prompted many automakers such as Japan's Toyota Motor Corp to say at the time that they would look at adjusting their retail prices in China to provide competitive offers to customers.
However, firms affected by the higher duties on cars imported from the U.S. such as BMW AG and Ford later decided to take a profitability hit rather than raises prices fully on U.S.-produced SUVs.
Reporting by Sun Yilei and Brenda Goh.