Saudi national Nahid Almanea, 31, was stabbed 16 times as she walked to the University of Essex campus last June.
James Attfield, 33, was found with 102 knife wounds in Castle Park last March.
Essex Police said the boy, from Colchester, was arrested on Tuesday on Salary Brook Trail on suspicion of carrying an offensive weapon. He was then arrested over the murders.
The boy was arrested on the same footpath where student Ms Almanea was killed on 17 June, as she walked from her student accommodation in Woodrow Way to the university complex in Wivenhoe.
He is currently in custody at the town's police station.
Police have previously said there could be a link between the two murders, but both killings were so vicious they could not tell if the same weapon was used.
Mr Attfield, who was known as Jim, was found on the Riverside Path in Colchester in the early hours of 29 March with dozens of stab wounds to his body.
Essex Police said "inquiries are continuing", and added that they would "like to hear from anyone who may have any information in relation to the investigation".
A 16-year-old boy has been arrested over the murders of two people in Colchester.