The Mexican hosts edged the shootout 3-2 after the sides had ended 90 and then 120 minutes deadlocked. Mexico had gone into the half-time break a goal to the good thanks to Claudia Ericka Garcia but a second half equaliser from Raquel Rodriguez forced the game into a dramatic half-hour of extra time.
That excitement began with another goal from Rodriguez, which looked to have won it for Costa Rica, but Dinorah Garza popped up in the dying minutes to force the fateful shootout.
The final, meanwhile, was decided by a solitary Karla Schacher
goal that secured gold for Canada and left the American favourites
The CONCACAF trio complete the 16-team line-up for Chile 2008, with Mexico, USA and Canada joining the hosts, Argentina, Brazil, France, Germany, England, Norway, Nigeria, Congo DR, Japan, China, Korea DPR and New Zealand at the U-20 women's showpiece.