Meghan looked radiant in a simple yet elegant blue shirt dress, which retails for $840, by American label Veronica Beard, while Harry was dressed smartly in a navy button-up shirt and beige chinos.
The pair, who are expecting a child of their own in the spring, were serenaded by students at Tupou College, and called in at the Royal Palace, feted everywhere by excited crowds waving flags and signs celebrating the visit.
Sergeant Talaiasi Labalaba, of the Special Air Service (SAS), single-handedly held off 250 insurgents with a 25-pounder field gun after being shot in the jaw during the battle in Oman in 1972.
After the ceremony, the President of Fiji, Major General Jioji Konrote, gave a short speech thanking the royal couple for their visit and congratulating them on their baby news.
"Our two families have enjoyed a deep and warm friendship over many years and I hope that our close relationship continues with the next generation".
According to Page Six, the former Hollywood lighting director said that hearing the pregnancy news was a "very proud moment", and he looks forward to seeing a little Meghan or little Harry.
Meghan has been given the nickname "Di 2" by members of the royal household because of the similarities between her and Diana, sources say.
Tonga, home to just 106,000 people, is also known as the friendly islands.
The royal couple were also gifted with garland necklaces made from Fa and Puatonga flowers, which Meghan wore over her olive-and-white striped cotton dress by Australian designer Martin Grant.