Context Indigenous people influenced fire in Australia's deserts for millennia, until colonisation interrupted traditional fire practices. Many groups are reinvigorating those practices to achieve inter-linked biodiversity, cultural, and social benefits. Contemporary fire management integrates modern planning and delivery approaches with cultural process. However, deserts have changed since colonisation (e.g. invasive species, biodiversity loss, climate change) and fire-management outcomes for Country are less certain. Some Indigenous groups are integrating scientific methods into their programs, to examine biodiversity outcomes and refine management.Aims Karajarri and Ngurrara Traditional Owners wanted to understand how fire affects Kuwi (mammals, reptiles) on their Country, to guide fire management. Karajarri and Ngurrara Rangers worked together on this project, exchanging skills and knowledge with each other, and with scientists.Methods We established 32 monitoring sites at four locations on Karajarri and Ngurrara Country. We undertook 11 survey trips from 2018 to 2022, gathering data from 81 site visits. Using Landsat satellite imagery we described fire patterns around each site, focussing on seral stage (as defined by Traditional Owners), patch size, and seral diversity at small (500 m), medium (1 km), and large (5 km) spatial scales.Results There were 378 mammal captures (11 species) and 3392 reptile captures (66 species). Mammal species richness and captures were lowest in Wuntara (recently burnt) and highest in Nyirrinyanu (mature) spinifex. Mammal species richness increased with seral diversity within 1 km around the trapping site. Reptile species richness and captures were unaffected by seral stage. However, many species were caught significantly more often in specific seral stages. Neither reptile richness nor capture rate were related to patch size or seral diversity.Conclusions Retaining a mix of seral stages can maintain diverse reptile and mammal assemblages. The management challenge will be increasing the extent of mature/long-unburnt spinifex, currently the rarest seral stage. Ranger fire management has already reduced mean fire size by 40-52%, and further reductions are possible.Implications Our work improves the understanding of fire effects on northern desert fauna, guides management, provides important ecological information from a little-studied region of Australia's deserts, and increases the recognition of Indigenous conservation management of Country. Karajarri and Ngurrara Rangers collaborated with scientists to investigate how fire management in the Great Sandy Desert could help mammals and reptiles. We found that some species prefer particular spinifex post-fire ages, from recently burnt to long-unburnt, and that patchworks of spinifex ages benefit mammals. This means that we should aim to reduce fire size and increase the area of mature/long-unburnt spinifex. Our work provides ecological information from a little-studied region of Australia, and highlights the role of Indigenous land managers in biodiversity conservation.Translated summary: The two ranger groups have decided not to translate the summary into their languages. Although there are many language speakers from Ngurrara, the most fluent Karajarri speaker passed away last year, and translating complex sentences is now challenging. Out of mutual respect for their collaboration, the rangers prefer not to include a summary that is only in a Ngurrara language. However, we use words from both languages in the text below. A short video about our project can be seen here. Photographs by Anne Jones.This article belongs to the Collection Indigenous and cross-cultural wildlife research in Australia.