John Leggott College in Scunthorpe has has a positive case of coronavirus, who is now self-isolating at home.
The college West Common Lane has not said whether or not the case is a member of staff or a student.
Everyone who has been in close contact with the individual affected has been told, which is allegedly a small bubble of 11 people.
The college said: “With nearly 2,000 people in our community, we recognised that a positive test was always a possibility, so before reopening this month we put things in place to reduce the risk of infection as far as we could.
“As a result of the positive test we have now put further response plans into action.”
More than 25 schools in Greater Lincolnshire have been affected by COVID-19 since term started.