This paper reports thrips (Thysanoptera) cross-pollination in the primitive angiosperm, Popowia pisocarpa (Annonaceae), in lowland rain forest of Sarawak, Malaysia. Flowers of P. pisocarpa have a tiny pollination chamber (3–4 mm in depth) with the entrance almost closed by the disk-shaped stigmatic heads, allowing only small insects to enter. Experiments showed that thrips were effective pollinators and flowers ofP. pisocarpa were self-incompatible. Seed set was limited by pollen. Clumped adult trees had higher seed-set than more distant individuals (>5 m from nearest flowering neighbor), indicating limited inter-tree movement by thrips.