Utricularia caerulea was among the first seven widely distributed species of Utricularia described by Linnaeus in 1753. To date, this Old World species is known to occur from Madagascar to Japan to Australia. It is rather variable throughout its range, and therefore worldwide has more than 30 synonyms.

It is almost always found growing together with other Utricularia species, sometimes with their stolons and leaves inseparably entwined and forming dense vegetative mats over the wet substrate. The leaves are narrowly obovate, and grow in a lax rosette at the base of the peduncle. The racemose inflorescence is rather slender and tall, with buds, flowers and fruits that are more or less crowded near the tips, which may twine a little in some individuals. The flower has a broadly ovate lower corolla lip with a conical spur parallel to it, topped with a small, oblong and erect upper lobe, and completed with two conspicuous yellow to orangey spots at the base of the lower corolla lobe marking the entrance to the spur. With some imagination, the flowers appear to resemble a hat-wearing, cartoon duck character!

In Peninsular Malaysia, there are two flowering forms. The white form is always found near coastal or in lowland heath vegetation or other wet habitats with open, sunny conditions. Rapid development in the coastal lowlands in the Peninsula since the 1980s has affected many habitats of the white-flowering form. Although formerly recorded as common, it has now become rare and during recent surveys it was only found from one inland heath. In Peninsular Malaysia, the pink form is restricted to riverine open areas or heath vegetation in the hills. So far it is known from only two sites, Gunung Jerai, Kedah, and G. Ledang, Johor, but it was not relocated from the former on recent trips. Currently the species is given a ‘Vulnerable’ conservation status.