Millets Farm garden centre near Abingdon is to hire a security guard after being broken into three times this month.
In the latest incident on Monday night, thieves attempted to steal a safe at the Frilford centre and made off with petty cash.
The culprits forced their way in through the front door at about 10.30pm then broke into the office, say?Thames Valley Police.
In an attempted burglary on Friday, August 1, offenders tried to take a safe from the shop at 1.50am but ran off when they were spotted.
Police have not yet revealed the details of an attempted break-in on Thursday, August 14.
No one has yet been arrested in connection with any of the incidents.
Millets Farm employee Matthew Moran said: ?I think they are probably quite intrigued about what is in the safe.
?They will get a nasty surprise because it?s just paperwork.?
He said the centre would be taking on a security guard to patrol the premises at night with a dog and install new security cameras.