Bainimarama was in London to attend the 52nd session of the International Sugar Organisation.
"It was an honour to be among the first to personally congratulate His Royal Highness, Prince Harry of Wales, on his engagement, where we discussed our shared passion for causes like education, the environment and rugby," Bainimarama said in an online posting.
At the meeting, Bainimarama told Prince Harry there were new opportunities for cooperation between Fiji and the United Kingdom.
He also acknowledged Prince Harry for his work in assisting the development of young people in vulnerable communities around the world.
Prince Harry, in turn, congratulated Fiji for winning the Rugby Sevens Gold medal at the 2016 Rio Olympic Games.
He said he was a keen follower of Fijian rugby and was passionate about watching Fiji play.