After establishment of Azerbaijan Democratic Republic on 28 May 1918 he worked as the Director of State Issues Department of Council of Ministers of ADR. When his brother Fatali Khan Khoyski formed the third cabinet of ADR, Rustam Khan was appointed the Minister of Social Security. After Bolshevik take over of Azerbaijan, Khoyski remained in the country and served as Chairman of the Azerbaijan SSR Economic Council Board. In the following years, he also worked as a corporate lawyer in Baku and Moscow.