Fiji lost the opening match of its northern hemisphere rugby tour when it was out-Fijied by the Barbarians 40-7 on Friday.
In the rain, the Barbarians opened with a try from a lineout maul, then sliced apart the Fijians to lead 28-0 in 28 minutes.
Fiji was more competitive in the second half, and Waisea Nayacalevu crossed, but hooker Akker van der Merwe and replacement back Luke Morahan both scored their second tries for the Baa-baas in a grand display in poor conditions.
Robert du Preez converted five of the six tries for the Baa-baas, whose victory capped a memorable week, including drawing with South Africa 31-31 last weekend, and beating the Czech Republic 71-0 on Tuesday.
The Baa-baas were mainly Super Rugby players who added former All Black prop Ben Franks and Ireland winger Tommy Bowe, making his debut in the invitation team's first match in his Belfast hometown in 59 years.
Fiji move on to play England next weekend, then Japan in France.