When she found Picoly, a Jack Russell, in distress in the water, she threw herself into the lake fully clothed to rescue him.
A security agent who refused to help rescue the dog was dismissed from their post after the 22 April incident.
Mrs Temer had been walking in the gardens with her son, Michelzinho.
When Picoly took an interest in the lake, he dove in and could not return to shore.
Brazil's President, Michel Temer, and his family have two dogs: Picoly and Thor, a golden retriever.
Brazil's First Lady, Marcela Temer