The victims, identified as Dharmesh Thakkar, a local journalist, his wife Garima and son Akshyae, are recuperating at Hinduja Hospital.
The incident occurred last night and the police suspect robbery as the motive.
The domestic help, who is absconding, could not be immediately identified as the family is still under treatment and their statement is yet to be recorded.
Police suspect the servant, hired just a month back, mixed juice of 'Datura' (a poisonous flowering plants) in the food he cooked for the family last night, following which they passed out.
A case under sections 328 (causing hurt by means of poison, etc.) and 381 (theft by clerk or servant of property in possession of master) of IPC was registered by Khar police.