He was married three times: firstly to Natalia Yakovlevna Evreinova (1732-1756), secondly to Maria Sverchkova (1644–1776) and thirdly to Alexandra Evtikhievna Safonova (1745-1778).

[1] His children from the first marriage were: From the third marriage: Inheriting mines and metallurgical factories in the Urals and Siberia, he was also a major landowner, with properties in central and southern Russia and in Italy.

He left eight metallurgical factories, a huge annual income and 12,000 serfs to his son Nikolai on his death.

[3] He was an amateur scientist, the first member of the Demidov family to protect the arts actively and a major traveller, journeying abroad to see Europe's industrial innovations, manners and culture.

In 1779 he set up a medal to reward a success in mechanics, to be decided by the Russian Academy of Sciences.