Public Health England says it has been notified of three confirmed and six probable cases of measles in children and young adults in the Gloucestershire area.
PHE is asking parents to check that they and their children have received two doses of Measles, Mumps and Rubella (MMR) vaccine.
It also says people should be aware of the signs and symptoms of measles.
Symptoms of measles can include cold-like symptoms, sore red eyes, a high temperature or a red-brown blotchy rash.
An MMR catch-up immunisation campaign was launched in 2013, targeting unimmunised and partially immunised adolescents aged 10 to 16 years.
90 cases were confirmed in England in 2014, and 59 cases in 2015.
There was a sharp increase in 2016 when 318 confirmed cases of measles were reported.