The first division club said the president would play for about 20 minutes per match but not in each game, owing to his busy schedule.
He will receive the minimum salary, about $214 (£127).
“He loves football and plays well,”
said Sport Boys’ president Mario Cronenbold.
“He’ll wear the No 10 shirt.We’ll send him a list of matches and he’ll chose which ones to play in,
” he said.
A local politician with the governing MAS party (Movement towards Socialism), Edwin Tupa, said playing with a professional football club is a dream come true for President Morales.
The president is said to be fit and very excited with the prospect of playing.
Mr Morales has played in several well-publicised matches with journalists, union leaders and other presidents.
In 2007 he played a match at 6,000m (19,700 ft) above sea level in a protest against efforts to stop Bolivia playing its international fixtures at high altitude.
And in 2006 he suffered a broken nose in a clash with a goalkeeper.