Apiarist Murray McGregor, the owner of Denrosa Apiaries in Blairgowrie, pled guilty to administering "unauthorised veterinary medicinal products".
The 61-year-old has produced honey for both the Balmoral Estate and Prince Charles' Duchy Estate.
He admitted committing the breach between July 2009 and October 2010.
During the period, McGregor admitted importing the unauthorised medicinal product, Terramycin 100MR.
He also admitted giving Terramycin 100MR to an animal, namely the honey bee, in contravention of the relevant regulations.
He admitted a third charge of possessing the substance without authorisation.
Perth Sheriff Court was told that a further expert report on the case was being prepared.
In 2009, a bee farm the Lothians owned by McGregor was targeted by thieves and 11 hives containing up to 500,000 bees were stolen.
The bees, which were being farmed under the Denrosa banner, were due to be transferred to the Balmoral Estate.
A Royal beekeeper has admitted giving a banned drug to his honey bees in what is believed to be the first case of its kind in the UK.