He was eligible to play for both England and Trinidad & Tobago. He initially represented England as both an U21, and on the bench for a full International against Chile, but in the end opted to play for Trinidad & Tobago. A dispute with the national team ruled him out of contention for several years, but he returned to play in the country's first ever World Cup appearance in 2006.
He is now working for sports news and broadcasting service ESPN and regularly commentates on Serie A and Spanish Primera Liga matches.
He was instrumental in Reading's rise from the old Second Division to second place in the First Division, where he narrowly missed out on the Premier League following a 4-3 defeat to Bolton in the 1995 play-off final. Hislop was one of many Reading players to move that summer of 1995, signing with Newcastle United for £1.575m, a British record for a goalkeeper at the time.
Hislops first season at Newcastle was spent battling with incumbent goalkeeper Pavel Srnicek for the starting role. After starting strongly and being the starter through until December Hislop suffered an injury that allowed Srnicek to regain the starting role that he held for the remainder of the season as Newcastle blew a 12pt lead in January to finish the season 2nd.
In 1996/97 he remained on the bench, having to watch Srnicek tend the nets until approximately the same time the previous season. A perceived dip in form and a number of mistakes from Srnicek allowed Hislop to take the starting role back again and he made only his second league start of the year in a 7-1 defeat of Tottenham. Hislop successfully retained the starting position as Newcastle pipped Arsenal and Liverpool to 2nd place on goal difference at the end of the season.
Hislops role further came under threat when new manager Kenny Dalglish opted to purchase a former player of his own from Blackburn Rovers. Shay Given cost £1.5m and a season-long battle for the no.1 spot ensued. Shay initially started the season, but after a string of defeats and 5 games without a win Dalglish went back to Hislop in November and he stayed there until injury in February allowed Given back into the frame.
With his contract running out, and having not yet managed to play a full season at Newcastle Hislop chose to leave on a free transfer. West Ham had operated a "goalkeeper by committee" approach the previous season seeing first Ludek Miklosko, then Craig Forrest then Bernard Lama hold the starting role. With Miklosko now with QPR and unable to secure Lama beyond his 3 month loan Harry Redknapp snapped up Hislop and installed him as first choice goalkeeper.
He returned the following year 00-01 but in a tumultuous season he saw his manager fired, and two of the clubs most promising players in Rio Ferdinand and Frank Lampard sold on. His performances were strong in an unsettled team. However new manager Glenn Roeder purchased the unsettled, and recently crowned heir apparent to the England No.1 jersey, David James from Aston Villa who had publicly fallen foul of his manager John Gregory. The deal was seen as a coup for West Ham, though it resigned Hislop to the bench for what was seen to be his final season with the club as James (a year younger) was intended to be the obvious longterm custodian.
However before the 01-02 season could even start James tore his knee ligaments on England duty after a collision with Martin Keown. The injury ruled James out for practically the first 3 months of the season. Hislop instantly stepped back into his starting role and kept five clean sheets in his 12 appearances that year for the club (though he also featured in the back to back drubbings from Everton 5-0, and Blackburn 7-1).
James reclaimed the starting role, and at the end of the season Hislop left the club on a free transfer.
In April 2005 Hislop was named the inaugural winner of the PFA Special Merit Award, for his services to football.
Following the appointment of a new manager in Alain Perrin, Hislop failed to regain his starting place in favour of ex Liverpool keeper Sander Westerveld, and when his contract expired in June 2005 he was released by the club.
He featured in every FA Cup game as the team made its way to the FA Cup final, and in all kept 7 clean sheets in 27 appearances.
The FA Cup final finished 3-3 after a late equaliser from Steven Gerrard in the 93rd minute (the Goal of the Season). Hislop saving Sami Hyypiä's penalty was not enough for his team as Liverpool won the game 3-1 on penalty kicks after Anton Ferdinand missed the final West Ham spot kick of the day.
Hislop left FC Dallas and retired from professional football in August 2007.
In 2005, Hislop was part of the Trinidad and Tobago side that qualified for the 2006 FIFA World Cup with a victory over Bahrain. The draw for the World Cup placed them in Group 2 alongside Sweden, Paraguay and England.
On 10 June 2006, Hislop was the starting goalkeeper for the first ever Trinidad and Tobago national team to compete in the World Cup. He was instrumental in securing a 0-0 draw against the heavily favoured Sweden, making several saves, even with his team down to ten men for almost the entire second half.