The slender-horned spineflower is found in coastal foothill drainages of Riverside, San Bernardino and Los Angeles Counties, ranging from Temecula to Santa Clarita. They are found east of San Bernardino along the Santa Ana River and along the southern portion of Cajon Creek.

Slender-horned spineflower is an annual herb that occurs on stable alluvium away from channels in areas with little flooding disturbance and infrequent water flows. They occur in slightly acidic silt soil with low salinity, little organic matter and low nutrient content. They bloom between April and June.

The primary threats to slender-horned spineflower are habitat loss and degradation, mining and flood control and other hydrologic alterations, off-highway vehicles and nonnative species. Management includes protection and could include habitat restoration and reintroduction.