Pennant was first selected to the Guatemala national team in 1969, appearing at the IV CONCACAF Championship that year. In 1971, he was a member of the national squad that attempted to qualify to the 1972 Olympic Games, without success. Four years later, however, he helped Guatemala qualify to the 1976 Games in Montreal, where he started against Israel (0-0), played the last 15 minutes of a 1-4 loss against Michel Platini's France, and the match against Mexico (1-1).