The silver and black Dawes deluxe 401 was taken from the rear of Brentwood Design Partnership on Belford Road sometime between 8am and 6pm on Thursday 3 November 2011.
The victim had left his bike there while he went to work and when he came to collect it following his shift, it had gone.
Officers are appealing to anyone who witnessed the theft or has any information that can help the investigation to come forward.
PC Leah Champion, of Harrogate police, said:
I am appealing to anyone who saw any suspicious behaviour in the area of Belford Road on Thursday to get in touch with the police or Crimestoppers.
I would also like to speak to anyone who has been offered a similar bike for sale recently.
Anyone who can help the police with their enquiries is urged to contact PC Leah Champion, of Harrogate police on 0845 60 60 24 7, quoting reference number 12110187134.
Alternatively, Crimestoppers can be contacted anonymously on 0800 555 111.