This book constitutes the refereed proceedings of the 24rd Brazilian Symposium on Formal Methods, SBMF 2021, which was held in December 2021. Due to COVID 19-pandemic it took place virtually. The 8 regular papers presented in this book were carefully reviewed and selected from 15 submissions. The papers detail the development, dissemination, and use of formal methods for the construction of high-quality computational systems, aiming to promote opportunities for researchers and practitioners with an interest in formal methods to discuss the recent advances in this area