Her work has often been identified by her use of cross-hatching and grid patterns, using a fine marwat (a brush made of hair). These patterns embody the freshwaters and estuaries of her homeland, Wäṉḏawuy. The grid makes reference to the landscape of Wäṉḏawuy - a network of billabongs surrounded by ridges and high banks. Its structure also has reference to a fish trap constructed by Ancestral Hunters who set a trap here to snare Mäna (the ancestral shark).

Marrnyula is an artist who has always pursued an individual style and has constantly evolved and adapted to limitations. As she began to struggle with mobility issues, she created installations of hundreds of small bark paintings pieced together called Muṉguymirri, which means 'in small pieces'. These large-scale polyptych works further expanded her abstracted view of both her identity and her surrounding landscape.

In 2019, Marrnyula was commissioned by the Kluge Ruhe (USA) for the exhibition, Maḏayin:Eight Decades of Aboriginal Australian Bark Painting from Yirrkala. The work of over 250 small barks was first exhibited at the Tarnanthi Festival in Adelaide, at the Art Gallery of South Australia, before it toured the United States and was most recently displayed at the Asia Society Gallery in New York City (2024).

Marrnyula Munuŋgurr is the daughter of renowned artists Djutadjuta Munuŋgurr and Noŋgirrnga Marawili. Wäṉḏawuy is her official homeland in which she first became an artist. She is a part of the Dhuwa moiety. Wäṉḏawuy is in an outstation belonging to the Djapu. It is freshwater, inland, and Mäṉa (the shark) is their totem. Marrnyula’s paternal grandfather was the Djapu clan leader and artist Woŋgu Munuŋgurr (c. 1880-1959) and her maternal grandfather was the Madarrpa leader and artist Mundukul Marawili.