The Grade II listed Greestone Building, in Lindum Road, had been modified to make way for the centre - the first of its kind in Lincolnshire.
The college will accommodate about 640 students studying science, engineering and maths, from September.
UTCs were created by the government to address the country's lack of qualified engineers.
People living nearby had claimed the redevelopment of the 19th Century building would be a "blot on the landscape".
However, contractor Willmott Dixon said it had been "sympathetically renovated" while preserving original features.
Principal Rona McKenzie said: "The old and the new have been brought together wonderfully and it feels like it's meant to be, the original and new building fit together perfectly."
Built in 1893, and designed by architect John Watkins, the Greestone Building was originally a girls' school and was later adopted by the University of Lincoln.
Work has been completed on a new £6m University Technology College (UTC) in Lincoln.