The purchase is the seventh by the firm since 2012, as it seeks to grow its occupational health division to provide nationwide coverage.
Headed up by its founder Dr Bryan Fehilly, who will remain with the business, Newhall provides occupational health and other medical services, as well as a private GP service and travel clinic.
It is believed that the new purchase will expand employment opportunities with the business.
BHSF Group chief executive, Peter Maskell said “We are very pleased to have acquired such a successful business which will strengthen our OH proposition and give us greater presence in the marketplace.
“Initially Newhall will be a subsidiary of BHSF Occupational Health Limited, which is headed by MD Dr Philip McCrea”.