The family alleges in their civil wrongful-death complaint that Xiaoye Wang's death could have been avoided if Bristol-Myers Squibb and the University of Medical Center at Princeton hadn't acted negligently.
Prosecutors say his estranged wife, Tianle Li, obtained thallium from her job as a chemist at the pharmaceutical company. Authorities say Li slipped the highly toxic metal in her husband's food between mid-November and Jan. 26, when he died at the hospital.
She has pleaded not guilty to murder and hindering apprehension charges.
The company and the hospital aren't commenting on the lawsuit.
The family hired a Philadelphia-based law firm.