Three bicycles with a combined value of around £1,500 were stolen from Lincoln Central railway station, prompting a police investigation.
British Transport Police is looking into the incidents, which happened earlier this month on March 9, 10 and 17.
On each occasion a man is reported to have entered the cycle hub at the station and stolen a bike.
British Transport Police released CCTV images on Thursday, March 26 of a man officers would like to speak to, who they believe may have information that could help with the investigation.
Anyone who recognises the man should contact BTP by texting 61016 or by calling 0800 40 50 40 quoting reference number 2000025689.
Alternatively, it can be reported through the independent charity Crimestoppers anonymously on 0800 555 111.