In 2015, Mercado was first in the FHM "Philippines' 100 Sexiest Women" list after Marian Rivera vacated the title. Before Mercado traveled to New York for the film PreNup with actor Sam Milby, she was surprised and given a plaque by publisher Aeus Reyes, Allan Altera, and GMA News reporter Nelson Canlas. On 11 July, Mercado participated in the two-part FHM 100 Sexiest party at the SMX Convention Center in the SM Mall of Asia.
Mercado played the lead role of Melanie "Mel" Fernandez-Dela Paz in the GMA series My Faithful Husband, which aired on 10 August 2015. Despite its success, the series was not extended due to scheduling conflicts with Mercado, who at the time was acting in two films, The Prenup and WalangForever. The series earned the lead actors multiple acting awards and nominations. After the commercial success of WalangForever, Mercado earned her second consecutive MMFF Best Actress award in 2015.