On January 9, 2013, it was reported that Sebei had signed with WWE. The following day it was specified that Sebei and WWE had agreed to a verbal deal that would be signed, after Sebei passed all drug and medical tests. On January 30, it was reported that Sebei had passed his medical tests and officially signed his contract with WWE. On February 13, Sebei made his debut for WWE's developmental territory NXT Wrestling, but did not wrestle. Sebei's NXT in-ring debut took place at a live event on March 7 in Tampa, Florida, where he wrestled a tag team match while working unmasked and under his real name.
Sebei eventually settled on the ring name of Sami Zayn. Zayn made his televised debut on the May 22 NXT by defeating two former champions in WWE, first defeating Curt Hawkins in the opening match and then challenging and scoring an upset win over Cesaro later in the show. The following week he took part in an 18-man battle royal to determine the number one contender to the NXT Championship, but was eliminated by Mason Ryan. On the June 12 NXT, Zayn suffered his first pinfall loss in NXT in a rematch with Cesaro. On the July 17 NXT, Zayn failed to win another number one contender match also involving Cesaro and Leo Kruger. On the July 31 NXT, Zayn teamed with NXT Champion Bo Dallas against Cesaro and Kruger; after Cesaro and Zayn brawled to the back, Dallas lost the match and later blamed Zayn for the loss. On the August 21 NXT, Cesaro defeated Zayn in a two-out-of-three falls match to conclude the feud. On September 6, Zayn made his WWE debut at a house show in his hometown of Montreal, where he defeated Cesaro. When Zayn targeted Dallas' NXT Championship, Dallas cost Zayn his match against Cesaro's fellow Real American, Jack Swagger. Dallas held an open challenge to determine the next title contender but banned Zayn from competing, so Zayn masqueraded as the masked El Local and defeated Dallas to earn his title shot. The match occurred on the October 16 NXT; General Manager JBL restarted the match when Zayn won despite Dallas' foot on the ropes, but not when Dallas sent Zayn into an exposed turnbuckle to retain his title.
After trying a Beat the Clock challenge with Adrian Neville by defeating Leo Kruger Zayn lost a number one contender's match to Neville on the November 27 NXT. Zayn moved on to feud with Kruger and the feud culminated in Zayn winning a two-out-of-three falls match on the January 1, 2014 NXT. After that, Zayn's obsession with his loss to Cesaro the previous year led to him challenging Cesaro to a rematch on the February 27 NXT Arrival; Cesaro prevailed again but showed respect to Zayn after the match.
|Male Wrestlers||Adrian Neville • Aiden English • Alexander Rusev • Bo Dallas • Corey Graves • Danny Burch • Konnor • Leo Kruger • Mason Ryan • Mojo Rawley • Oliver Grey • Sami Zayn • Sylvester Lefort • Tyler Breeze • Viktor|
|Female Wrestlers||Bayley • Charlotte • Jojo • Lana • Paige • Sasha Banks|