This book constitutes the refereed proceedings of the Second International Workshop on Human Brain and Artificial Intelligence, HBAI 2020, held in conjunction with IJCAI-PRICAI 2020, Kyoto, Japan, in January 2021. Due to the COVID-19 pandemic HBAI 2020 was held in  the year 2021 and transferred into virtual format.   The 11 full papers presented were carefully reviewed and selected from 12 submissions. The papers present most recent research in the fields of brain-inspired computing, brain-machine interfaces, computational neuroscience, brain-related health, neuroimaging, cognition and behavior, learning, and memory, neuron modulation, and closed-loop brain stimulation.