With the help of an official, Trump handed the 30-kilo, eagle-topped and specially-named US President's Cup to a victorious Asanoyama, a 25-year-old competitor who until now had been relatively unknown in the sport.
The presentation took place in the "dohyo," the name given to the centre of the wrestling arena in the venerated Japanese sport.
The event was the subject of great media attention in Japan as it is unusual for an official representative of the US to take part in such a spectacle.
Trump eschewed the tradition of sitting cross-legged on a cushion in favor of a low-backed seat in the stalls along with First Lady Melania Trump, Japanese Prime Minister Shinzo Abe and his wife Akie Abe.
The match took place at the Ryogoku Kokugikan arena, the country's foremost sumo wrestling stadium.
Following the bout, Asanoyama - real name Hiroki Ishibashi - said he was lost for words with pride for having received the trophy from Trump.
From the dohyo, Trump also gave the victor a certificate and praised the wrestler for his "outstanding achievement" in the tournament. Asanoyama notched 12 wins and only 2 losses.
Other foreign heads of state who have watched sumo matches in Japan include former French President Jacques Chirac, who handed the winner of the tournament the Chirac Cup.
Trump arrived in Japan on Saturday and is scheduled to leave on Tuesday.
Earlier in the day, he held his first informal talks with the Japanese prime minister during a round of golf in southwest Tokyo.
( With inputs from IANS )