The open access volume LNCS 11739 constitutes the proceedings of the 9th International Workshop on Socio-Technical Aspects in Security, STAST 2019, held in Luxembourg, in September 2019. The total of 9 full papers together with 1 short paper was carefully reviewed and selected from 28 submissions. The papers were organized in topical sections named as follows: Methods for Socio-Technical Systems focused on instruments, frameworks and re ections on research methodology and also System Security considered security analyses and attacks on security systems. Finally, Privacy Control incorporated works on privacy protection and control as well as human factors in relation to these topics.