Protected areas have been gazetted to protect natural resources and biodiversity, but evaluations of effectiveness rarely include measures of species population change. We compiled annual site-level spending and elephant population data for 102 protected areas conserving either savannah (Loxodonta africana) or forest (Loxodonta cyclotis) elephants, which showed a median annual population decline of −0.78% across the protected areas. Site-level population change was strongly associated with funding and government effectiveness. Annual funding deficits occurred in 78% of the protected areas, and when comparing necessary levels of annual spend to stabilize elephant populations, we estimate a US$1.5 billion annual funding deficit across all the protected areas. While financial investment can improve elephant conservation outcomes, there is still a need to identify where and how to best finance elephant poaching interventions, requiring a global commitment to improve the socioeconomic impacts of protected areas on local communities and reduce ivory demand.