The 39-year-old forward, who plays for Vasco de Gama in Brazil, will join the side for the 2005-06 Northern Counties Eastern League (NCEL) competition.
The 1994 World Cup winner is the second high-profile Brazilian international coaxed to the club by owner Simon Clifford.
Last year the Teesside businessman also persuaded former Brazil captain Socrates to join the club, which is based in a former pit village near Leeds in Yorkshire.
Clifford, who names a number of Brazilian players among his friends, owns a string of soccer schools in the South American country.
Romario, who was sacked by Fluminense before joining Vasco in January, last played for Brazil in a World Cup qualifier away to Uruguay in 2001.
Garforth are top of the NCEL Division One table, having won 16 of their 24 matches this season.
