This book constitutes the refereed proceedings of the 20th IFIP TC 14 International Conference on Entertainment Computing, ICEC 2021, which was supposed to take place in Coimbra, Portugal, in November 2021. The 26 full papers, 13 short papers and 11 other papers presented were carefully reviewed and selected from 84 submissions. ICEC brings together researchers and practitioners from diverse backgrounds to discuss the multidisciplinary intersection of design, art, entertainment, interaction, computing, psychology in the fields of gaming and entertainment computing.