Nightingale Hammerson is in "advanced discussions" over a merger with the Abbeyfield Camden Jewish Society, which operates a 12-flat home, Belmont Lodge, in Bushey.
In a statement on Wednesday, Nightingale said it had been approached by Abbeyfield.
"Trends in the provision of services for older people are changing. This, combined with the nature of the building, suggests that ACJS needed to consider alternatives. These include the possibility of a merger with a larger organisation focused on providing services to older people in the Jewish community."
There were no plans to close Belmont Lodge - which currently has five residents - and residents' best interests would be the paramount concern. A further announcement was expected shortly.
Belmont Lodge opened in 2002. Its founding committee comprised representatives from a number of north London and Hertfordshire Reform and Liberal synagogues.