Vieira was raised in Portugal with his twin brotherRonaldo Vieira. He left Portugal in 2011 in search of more job opportunities for his family in England. Vieira began playing football in England with his brother for Whitley Bay Boys Club, a local team near Newcastle. Vieira then moved to Yorkshire and played 2 seasons in the Huddersfield Junior Football league for Batley Phoenix. Vieira then signed for York-based i2i Football Academy whilst studying at York College. He signed for Northern Premier League side Tadcaster Albion joining their academy. He went on trial at a side in the Czech First League and looked set to sign before interest from Leeds.
Leeds United
On 1 September 2016, he joined Leeds United on a one-year deal from Tadcaster Albion, joining his brother Ronaldo Vieira who was already a first team player at Leeds having made his debut in 2016. With Romario set to link up initially with the Under 23 side. After impressing for Leeds Under 23s side. On 31 January 2018, Vieira was named on the substitutes' bench for Leeds for the first time against Hull City in Leeds' 0-0 draw, in the process Ronaldo and Vieira became the third set of brothers to ever feature in a match day squad for Leeds United after Eddie and Frank Gray, and Ray and Rod Wallace He was again named on the bench in the following game, this time in a 1-4 loss against Cardiff City, the match proved to be the last of then head coachThomas Christiansen who was sacked after the game. On 18 May 2018, in Leeds' retained list for the 2018/19 season, Leeds announced they would not be renewing Vieira's contract and he would be released upon expiry.
Vieira was eligible to represent Guinea-Bissau, Portugal or England having been educated in the country for five years before the age of 18. After deciding to represent Guinea-Bissau at international level, he was called up to the national team. On 22 March 2018, Vieira made his debut against Burkina Faso as a substitute in a 2-0 loss.
Personal life
Vieira moved to Portugal at the age of five, shortly after the death of his father. Vieira was named after Brazilian footballerRomário, with his twin brother Ronaldo Vieira named after Brazilian footballer Ronaldo. Ronaldo is also a footballer and plays at Sampdoria. His twin brother Ronaldo represents the England U21s after he decided to represent England.