This workshop provides opportunities to exchange new ideas establish business or research relationships and find global partners for future cooperation. International Program Committee has 18 members. 100 % of ITTAP-2021 International Program Committee members have more than 10 DBLP papers. There are the representatives of 3 Ukrainian Universities and of 6 Universities from around the world (Germany, Sweden, Slovakia, Egypt, Poland, and Greece). 1st International Workshop on Information Technologies: Theoretical and Applied Problems (ITTAP-2021) received 49 submissions from Ukraine and the world. All papers were evaluated by two or three reviewers. Based on the reviews, a rating of papers was compiled. Papers with a positive average scores were accepted for presentation at the Workshop. According to the decision of the International Program Committee, 37 papers were conditionally accepted for presentation at the workshop. We received camera-ready papers, which were also evaluated by reviewers (it was checked whether all comments and recommendations were taken into account). As a result, only 37 camera ready papers are accepted for presentation at the Workshop. The ITTAP-2021 joined scientists from Ukraine, Indonesia, Slovakia, Morocco In general, the representatives from 3 Universities from around the world, and 25 Ukrainian Universities will take part in the workshop. So, final acceptance rate is 76%. We would like to thank the members of International Program Committee and Organizing Committee, and external reviewers for their excellent and tireless work. We sincerely wish everyone fruitful work and interesting presentations! We hope that the workshop results make a significant contribution to the development of intelligent information technologies in Ukraine and the world.