Ehsan Hajsafi gave Iran a lead in the second minute of first-half stoppage time after Trinidad failed to clear a corner kick by Fulham's Ashkan Dejagah.
Reza Ghoochannejhad doubled the lead five minutes into the second half.
Iran captain Javad Nekounam's penalty kick early in the second half was saved by goalkeeper Jan Michael Williams.
Iran opened its World Cup preparations with three friendlies in Austria, 0-0 draws against Belarus and Montenegro, then a 1-1 draw with Angola.
The Persians will open their World Cup campaign against Nigeria on June 16 in Curitiba.
The Iranian football team is also scheduled to face Argentina on June 21 and Bosnia and Herzegovina, June 25.