On 13 March 1937 he married nurse Ila Brenda Greig at Darlinghurst, and was thus estranged from his Jewish mother.

He spent several years in New Zealand before returning to Australia; he was admitted to the New South Wales Bar in 1940.

After Curtin became Prime Minister, Falstein openly clashed with him over issues concerning the Royal Australian Air Force in 1944.

Falstein had enlisted in the RAAF on 18 July 1942; he was convicted of using insubordinate language to a superior in September of that year and was sentenced to twenty-eight days detention.

In his final years he suffered from hypertension and diabetes, and he died on 18 May 1967 of cerebral thrombosis at Concord.