The conservation of rare and imperiled species is an iterative process requiring repeated efforts to identify knowledge gaps, collect empirical data, and implement policies to support species’ recovery and persistence. Humboldt martens (Martes caurina humboldtensis) are a rare and behaviorally cryptic carnivore that occur in coastal forests of California and Oregon. Humboldt martens were thought to be extirpated until 1996. Subsequently, Humboldt martens, and the analogous coastal distinct population segment of Pacific martens, were listed as state endangered in California in 2019 and federally threatened in 2020. Nonetheless, persistent gaps in knowledge remained regarding the abundance and distribution of Humboldt martens at the time of their listing. From 2022 to 2024, we collaborated with Tribal, state, federal, academic, and non-governmental institutions to survey for Humboldt martens within the Northern Coastal California, Southern Coastal Oregon, and California-Oregon Border extant population areas. We detected 46 (28M:18F), 12 (7M:5F), and 15 (11M:4F) unique martens within the population areas, respectively. Martens occurred across a range of vegetation conditions, including within the post-fire matrix resulting from the 2023 Smith River Complex. While our work filled some persisting knowledge gaps, we highlight continued survey efforts and conservation opportunities to support Humboldt marten recovery.