Thanks to the win, the 20-year-old has secured a place in the International Chopin Piano Competition, which will be held in the Polish capital later this year.
Second-prize winners Piotr Pawlak and Adam Kałduński have also booked their places in the upcoming international event, whose preliminary round saw judges evaluating video recordings submitted by more than 500 pianists from around the world.
Of this, a total of 180 pianists will be invited to Warsaw to perform in the event's qualifying stage before the final pool of 80 participants is selected for the competition, which is due to be held in October.
Founded in 1927, the International Chopin Piano Competition in Warsaw is among the most prestigious events of its kind worldwide.
Poland’s National Chopin Institute, which is the main organiser of the event, has hinted that the competition’s qualifying stage, originally scheduled for April, could be held at a later date if prospective participants from Asian countries face difficulties in reaching Warsaw due to the coronavirus epidemic.
Poland's Alexewicz is a student at the Music Academy in the southwestern city of Wrocław. He has previously won prizes at piano competitions in the Netherlands, Germany and France.
A total of 29 pianists took part in Poland’s National Chopin Competition, which ended on Sunday.
No third prize was awarded this year.