Abstract: During May to July, 2006 and April to May, 2007, we studied pollination biology in Ipomoea cairica, an invasive weed in Guangdong Province, China. Ipomoea cairica is a perennial creeping or climbing herbaceous vine, blooming all year round in Guangdong. The flowers gathered in cymes, with a purple or bluish purple bell-formed corolla. The petals unfolded at about 4:30–5:20 and closed at 17:40, lasting for about 12 hours. The proximity of the stigma and anthers during flowering period facilitated the transfer of self-pollen. The mean volume of nectar per flower was 5.82 ± 2.47 μL (n = 10), with a sugar concentration of 41.03 ± 6.52% and an amino acid concentration of ca. 0.042 mg/mL. During anthesis, both pollen viability and stigma receptivity remained at a high level (>90%). The mean P/O ratio was 4,778.18 ± 264.58 (n = 10). Carpenter Bees (Xylocopa sp.) were considered as effective pollinators, while flies and butterflies were occa-sional visitors. Ipomoea cairica is self-incompatible as determined by an absence of fruit set in the flowers following controlled hand self-pollination, producing fruits and viable seeds only after cross-pollination.