Of her 192 international career caps, Chastain played 89 primarily as a defender but occasionally as a midfielder. On June 1, 1988, she earned her first cap for the United States women's national soccer team during a match against Japan. She scored her first international goal on April 18, 1991. After coming in as a substitute forward, she scored five consecutive goals in the team's 12–0 win against Mexico during the 1991 CONCACAF Women's Championship.