Two bikes were stolen from the roof rack of a car parked in Oxford Street, Wellingborough.
The bikes were stolen from the vehicle sometime between 7.30pm and 11.35pm on Sunday, May 15.
Both were grey Trek FX 7.4 bikes; one was 25 inches and the other was 17.5 inches.
Officers would like to speak to anyone who witnessed the theft or has any information about it.
They can contact police on 101 or Crimestoppers anonymously on 0800 555111.