Maleno works for the NGO Caminando Fronteras which alerts naval authorities on migrant boats in distress at sea as they attempt the perilous crossing between Morocco and Spain.
She had been under investigation in Morocco since 2017 for alleged collusion in people traffickers offences after a similar case in Spain was dismissed.
Maleno told AFP she has received written notification confirming the decision of an appeals court in Tangiers, where she is based, to drop the case against her.
"The decision sets a precedent because it says that we must defend the right to life... (and) this is what we do," she said of her work with Caminando Fronteras.
"I always had faith in the Moroccan justice system because I always believed in my innocence," added the 48-year-old Maleno.
Her case had seen an outpouring of support from rights groups, politicians and celebrities such as Hollywood actor Javier Bardem.
Miguel Jesus Zea, head coastguard for the southern Spanish region of Almeria, said last year that Maleno had helped rescue tens of thousands of people off the coast of Almeria.