This book constitutes the refereed proceedings of the 26th International Symposium on Model Checking Software, SPIN 2019, held in Beijing, China, in July 2019. The 11 full papers presented and 2 demo-tool papers, were carefully reviewed and selected from 29 submissions. Topics covered include formal verification techniques for automated analysis of software; formal analysis for modeling languages, such as UML/state charts; formal specification languages, temporal logic, design-by-contract; model checking, automated theorem proving, including SAT and SMT; verifying compilers; abstraction and symbolic execution techniques; and much more.