Citing threat to his life, Mr Vamsi Mohan, a realtor from Jubilee Hills, had recently engaged three private security guards, Pankaj Prakash, Manish Thakur and Naresh Kumar.
The trio had come to the city three weeks ago and they hold gun licenses valid throughout the country, Nampally police said.
Mr Mohan is an accused in a murder case registered by the SR Nagar police station in 1999.
The Nampally police inspector Umendar who was frisking the entrants to the court found .32 revolvers on each of the security guards.
They were immediately arrested by the police. Private security guards cannot carry their weapons inside a court, said police officials.
The private guards said they were accompanying Mr Mohan for the trial.
Police said that the guards were at fault as they had not deposited their weapons at the local police station despite a notification issued by the city police.