Nine prohibition notices were given out during the recent visit by Vehicle Examiners.
Two officers from Devon & Cornwall Police spent four days on the islands at the end of May for their annual inspection.
They checked a total of 61 vehicles across the islands and took nine of them off the road.
On St Mary's, 23 were checked, with three PG9s (prohibition notices) handed out. On Bryher, there was one PG9 out of 10 checked, St Martin's had five PG9s out of 17 checked, and St Agnes had no PG9s, with 11 vehicles checked.
Vehicles given a prohibition notice have to be repaired and checked by police before they are allowed back on the road. The examiners are expected to return in September to double check the work has been done satisfactorily.
PC Lisa Woolley said: "One was a forklift on St Martin's. The rest were things like bald tyres, exhausts, minor things really."