His main assets were good set pieces and passing skills. After starting out at Sporting he moved abroad at the age of 19, going on to have unassuming spells in England (Newcastle United) and Spain (Valencia) before settling back in his country with Braga. He amassed Primeira Liga totals of 165 games and 23 goals, over the course of six seasons.
Viana represented Portugal in two World Cups and Euro 2012, also appearing with the under-23s at the 2004 Summer Olympics.
Born in Barcelos, Viana started his professional career at Sporting Clube de Portugal where he won the Young European Footballer of the Year award, after an excellent debut season in the Primeira Liga and, aged 19, was signed by Newcastle United from the Premier League for €12 million, joining former Sporting manager Bobby Robson and being tutored by veteran midfielder Gary Speed. He scored four goals across all competitions during his spell at St James' Park, against FK Željezničar Sarajevo and Feyenoord in the UEFA Champions League and Birmingham City and West Bromwich Albion in the league.
However, Viana was unable to cement a starting XI position, and returned to Sporting on loan. In his return he found his old form and enjoyed a successful spell, even helping the Lions to the campaign's UEFA Cup final.
At the start of 2005–06, Viana moved to Valencia CF, again on loan. In March 2006, reports stated that he had been signed him on a permanent deal for £1.5 million. During his first season he struggled to claim a first-team spot, facing tough competition from the likes of David Albelda and Rubén Baraja, manager Quique Sánchez Flores' preferred duo; still, he featured in 19 league games, and displayed some flashes of talent that allowed him to preserve his place in the Portuguese national squad.
In a bid to secure first-team football, Viana decided to join fellow La Liga side CA Osasuna on loan, on 13 July 2007. However, a serious injury during pre-season forced him out for four months. After recovering, he still featured in all of the last three matches, helping to a narrow escape from relegation.
In 2008–09, Viana took absolutely no part in coach Unai Emery's plans, being restricted to four UEFA Cup matches and two appearances in the Copa del Rey.
On 31 July 2009, Viana was loaned to S.C. Braga for one season, thus returning to Portugal after three years. As the Minho club led the league in its early stages, he scored his first goals upon returning to his country, hitting twice in a 3–1 home win against C.F. Os Belenenses, on 30 August. On 31 October, he again found the net, from a stunning free kick against S.L. Benfica in a 2–0 home triumph where he received Man of the match accolades) – Braga eventually finished in a best-ever second place, losing the title to precisely this team, in the last matchday, with the player appearing in 28 matches (14 as a reserve – he lost his importance after the return of Uruguayan Luis Aguiar, on loan).
In the 2010–11 season, under the same manager, Domingos Paciência, Viana regained his starting position over Aguiar, whom eventually left the club. On 6 March 2011, again from a direct free kick and against Benfica, he equalized for the hosts, in an eventual 2–1 home win; he also appeared in nine games (all starts) in Braga's UEFA Europa League runner-up run.
On 27 November 2011, in a game against FC Porto, Viana displayed a white T-shirt with the words 'Gary – Rest In Peace', in a tribute to Speed, who had committed suicide earlier that day.
On 5 June 2013, Al Ahli Club from Dubai announced the signing of Viana effective as of 1 July, when his contract with Braga expired. He made his debut on 30 August in the year's Arabian Gulf Super Cup at the Mohammed Bin Zayed Stadium, a penalty shootout victory after a goalless draw against Al Ain FC; his performance was described as "quiet" by The National, who attributed it to his unfamiliarity with the heat of the Middle Eastern summer. He totalled 39 appearances and three goals across his first season, helping the team conquer a domestic treble after adding the UAE Arabian Gulf League and the UAE League Cup.
Viana agreed to a deal with Al-Wasl F.C. of the same city and league, but the transfer was one of several declared void by the UAE Football Association for missing the 3 October 2014 deadline. It was completed the following 19 January. After leaving the club, he retired at age 33 on 13 October 2016.
Viana made his debut in the national team on 14 November 2001, in a 5–1 friendly win over Angola. Replacing suspended Daniel Kenedy in the last minute, he was a non-playing squad member for Portugal at the 2002 FIFA World Cup and played for his country at the 2004 Olympics.
Viana returned to the national squad after UEFA Euro 2004, and appeared in two matches (as a substitute) at the 2006 World Cup. He was called as a last-minute replacement for injured Carlos Martins to the Euro 2012 squad, with the team already in training camp.As of 1 July 2016
Primeira Liga: 2001–02
Taça de Portugal: 2001–02
UEFA Cup: Runner-up 2004–05
Taça da Liga: 2012–13
UEFA Europa League: Runner-up 2010–11
UAE Arabian Gulf League: 2013–14
Arabian Gulf Super Cup: 2013
UAE League Cup: 2014
Medal of Merit, Order of the Immaculate Conception of Vila Viçosa (House of Braganza)