Fanene was born in Sydney, Australia and raised in Honolulu, Hawaii. She also spent time in San Diego, California. She is the daughter of Joseph and Renate Fanene. She attended Palomar College in San Marcos, California, where she played college basketball. Prior to professional wrestling, Fanene was a plus-size model.
She was signed by WWE in early 2014 and was assigned to their developmental territory NXT, based at the WWE Performance Center in Orlando, Florida. She made her in-ring debut on May 7, 2015 at an NXT house show under the ring name Zada, where she and Devin Taylor were defeated by Bayley and Carmella in a tag team match. In August, her ring name was changed to Nia Jax.
After a series of introductory vignettes throughout September, Nia Jax made her debut on October 14 episode of NXT, defeating Evie in a singles match. Following her debut, she was shown as a monster heel who went on a winning streak, defeating various enhancement talents and NXT Diva Carmella. In November, Nia Jax formed an alliance with Eva Marie, and started her first feud with Bayley over the NXT Women's Championship. Nia earned a title match on December 16 at NXT TakeOver: London but was unsuccessful in winning the title.
On January 27, 2016 episode of NXT, Nia Jax returned to the ring after a month of inactivity due to a storyline injury, with a win over Liv Morgan. On February 10 episode of NXT, Nia Jax assisted Eva Marie in an attack on Bayley and Carmella after their championship match, until Asuka made the save, which led to a tag team match on February 24 episode of NXT, where Nia Jax and Eva Marie scored the victory. On 25 May episode of NXT, Nia Jax won a triple threat match over Alexa Bliss and Carmella to become the number one contender to Asuka's NXT Women's Championship. Nia Jax lost her title match at NXT TakeOver: The End. On July 20 episode of NXT, Nia was defeated by Bayley. On December 28 episode of NXT, Nia Jax lost to Asuka for the NXT Women's Championship in her last match in NXT.
Shortly after being drafted from NXT to the Raw brand as part of the 2016 WWE draft, which took place on July 19, 2016, Nia Jax started a winning streak against various competitors. In September, Nia Jax was placed in her first feud with Alicia Fox, which led to a match between the two on September 12 episode of Raw, that ended in a no contest after Nia speared Alicia through the ringside barricade. In a rematch between the two, which took place at the Clash of Champions pre–show, Nia then defeated Alicia via pinfall. On November 20, at the Survivor Series pay–per–view, Nia was a part of Team Raw in a elimination tag team match and was eliminated via submission by Becky Lynch.