Berekum Chelsea FC said in a statement that "masked men wielding guns and assault rifles" fired on the team bus and forced the players to take cover in the bushes.
The robbery, according to Ghana police, occurred around 22:30 local time (23:30 BST) along the Ahyiresu-Kwame Dwumor Sreso road in the Nyinahin District in the southern region of Ashanti.
Police said Frimpong sustained gunshot wounds and died in hospital while receiving treatment.
"Another victim, George Owusu Afriyie, 52, was also robbed of 4,500.00 cedis (£303)," the police said in a statement.
The Ghana Football Association described the incident as "tragic" and a "huge loss to Berekum Chelsea but also to Ghana football as a whole."
"Dominic was a promising young talent whose dedication and passion for the game embodied the spirit of our league," it said in a statement.
The 20-year-old forward joined Berekum Chelsea FC on loan from Aduana Stars FC at the beginning of the year.
He played 13 games and scored two goals for the club, according to local media.