Drosera sewelliae is a pygmy sundew known for its large, orange blooms. The species has among the largest blooms of the pygmy sundews, with a flower that often reaches a larger diameter than the rosette of leaves.

Drosera sewelliae is a small sundew with a rosette of flat-lying leaves around 2cm in diameter. The petioles are moderately thick and the laminae are oval-shaped. The flower is metallic orange in colouration with a black centre fringed with maroon and reaches up to 2cm in diameter. There are five styles that are long and thin. The stigmas are ball-shaped and black. The pollen is white.

The species grows in laterite substrates in well-lit open forest within the Perth Hills NE of Perth. The plants are commonly found in sunny clearings amongst sparse heath and also amongst leaf litter under the dappled shade of tall trees. It comes to bloom in spring and goes dormant during summer.

Drosera sewelliae is superficially similar to other orange-flowered pygmy sundews but is reliably distinguished by its floral structures. The combination of five styles with a globose stigma is unique amongst the orange-flowered pygmy Drosera.