The 35-year-old was recruited to the Spanish squad for her veteran experience which includes a silver medal at the Valkenburg 2012 road world championships.
Neylan, who leaves Orica-Scott after two seasons, will join the eight riders earlier announced to tackle Movistar's debut season in 2018.
They include Spaniards Mavi García, Eider Merino, Alicia González, Alba Teruel, Lourdes Oyarbide and Lorena Llamas along with Poland's Małgorzata Jasińska; and France's Aude Biannic.
"The opportunity to begin a new journey with Movistar supports my curiosity to embrace new challenges, and be the best athlete I can be moving forward," Neylan said.
"The Movistar Team has a sound philosophy to develop young riders, a role where I can give back, share my experience mentoring young women is a pivotal part of being an athlete and incredibly rewarding.
"I'm so happy to join the Movistar Team for 2018 and looking forward to pouring my passion and enthusiasm into a new and exciting project."
In addition to her world championship silver, Neylan has won the GP Plumelec (2016), the Cadel Evans Road Race (2015) and the Trophée d'Or GC in 2015.
She has been selected for four Australian world championship teams and was an Olympian in Rio 2016.