The win came in the right time for the Kenyan champions, who are also set to face rivals AFC Leopards in a derby on Sunday.
Midfielder Humphrey Mieno, who was crowned man of the match, is happy with the way his teammates played and the end result.
"It was not an easy match despite us winning 4-0; we have been doing everything right even in our past matches, the main problem has been on scoring goals.
"We have been creating many chances but finishing them was a problem, but against Yanga we did well and that made a difference at the end of the day.
"It is a motivation as we prepare to face AFC Leopards on Sunday, it is a psychological boost,” Mieno told Goal.
Gor Mahia are second in Group D with five points from the three matches.