Viliami worked with the Tonga Ministry of Agriculture, Forestry and Fisheries (MAFF) for 31 years. He looked after the entomology section within the Research Division and was promoted to role of Chief Entomologist.  Much of his entomology work focused on biological control and Integrated Pest Management approaches, with work on the Silverleaf Whitefly, Coconut Rhinoceros beetle, Diamondback moth and Spiraling Whitefly. He also focused on the epidemiology of viruses affecting squash crop production in Tonga.

Viliami was also Head of Quarantine Division for MAFF for eight years, where he was the National Plant Protection Organisation representative for Tonga, in addition to serving on the IPPC technical advisory committee for the Year of Plant Health 2020. During his time as Head of Quarantine he was involved with facilitation of agricultural trade, ensuring oversight of export pathways for root crops, horticultural crops and handicrafts, in addition to serving on the Tonga delegation in PACER (Pacific Agreement on Closer Economic Relations) Plus negotiations.