Two children who go to the Miles of Smiles nursery in Baglan have been confirmed as having the virus, while five others are being tested.
A vaccination session is planned at the nursery on Friday for children who have not had the MMR.
Parents who cannot attend should make an appointment with their GP.
Public Health Wales (PHW) said vaccination uptake at the nursery was good but some children were at risk because they were too young to have received one or both doses of the vaccine.
Last July saw the end of Wales' biggest outbreak of the infection in Swansea, which resulted in 1,200 reported cases and one death.
Dr JÃ¶rg Hoffmann, of PHW, said: "While two cases of measles may not sound a lot, we have five other children with symptoms, all attending a nursery school where there are children who are too young to be fully-vaccinated and could easily catch and spread measles."
He said parents in the wider Neath area should also get their children vaccinated.
Symptoms of measles include a fever, tiredness, runny nose, conjunctivitis and a distinctive red rash.
It is very contagious, can cause serious complications and in rare cases can be fatal.
Parents are being urged to get their children vaccinated following an outbreak of measles at a nursery school in Port Talbot.