The black-and-yellow broadbill breeds during the dry season throughout its range, with both sexes helping build a large, untidy, pear-shaped nest out of moss, fungal mycelia, and leaves.

The black-and-yellow broadbill was described as Eurylaimus ochromalus by the British naturalist Stamford Raffles in 1822 based on specimens from Singapore.

[5] Black-and-yellow broadbill is the official common name designated by the International Ornithologists' Union.

[7] The species is called takau kasturi in Malay, Nok Phaya Paak Kwaang lek in Thai,[8] and curɔɔw in Temiar.

[6] Based on a 2017 study by the Brazilian researcher Alexandre Selvatti and colleagues, its closest relative is the banded broadbill.

[10] An earlier 2006 study by Robert Moyle and colleagues also found strong support for these relationships, but did not sample the wattled broadbill.

[4][13] However, all of the species' populations show significant variation in appearance between individuals, making the recognition of subspecies inadvisable.

The iris is pale yellow, while the bill is bright blue, with a green tip to the upper mandible and black edges.

Juveniles lack a well-defined breastband and have a pale yellow supercilium (a stripe running from the beak to above the eye) with grayish-white underparts.

This song is similar to that of a banded broadbill, but is longer, accelerates more slowly, lacks an initial whistle, and ends suddenly.

[8] The black-and-yellow broadbill mainly feeds on insects, including orthopterans (grasshoppers, crickets, and locusts), mantises, beetles, hymenopterans (ants, wasps, sawflies, and bees), flies, winged termites, and caterpillars.

[15] The black-and-yellow broadbill forages in the middle and upper layers of forest in scattered flocks of ten to fifteen.

Individual birds feeding on exposed perches in the canopy may be acting as lookouts for larger, more dispersed flocks.

Nests are built by both sexes and are typically located at the edges of clearings or above streams in obstacle-free sites.

They are off-white to fawn pink with variable brown to purplish-brown flecking and underlying light purple spots.

In Borneo, black-and-yellow broadbills have also been observed defending their nest from Prevost's squirrels who were foraging on a nearby vine.

[8][19] In Thailand, the black-and-yellow broadbill has been recorded being parasitised by the chewing louse Guimaraesiella latirostris, of which it is the type host.

Its population is thought to be declining fairly quickly due to habitat loss caused by logging, land conversion, and wildfires.

It is likely to survive in the long-term only in protected areas and higher-lying forests in spite of its tolerance of degraded habitat.