Nicol was first capped at the senior level for Scotland on 12 September 1984, soon after becoming a first team regular for Liverpool. Jock Stein gave Nicol his international debut in a friendly with Yugoslavia. His debut was a memorable one, as he helped Scotland beat Yugoslavia 6–1 in a friendly at Hampden Park in front of a crowd of 18,512. Helping Nicol settle in with the national team were club mates Kenny Dalglish and captain Graeme Souness, who both scored. The last of his 27 full caps for Scotland came on 11 September 1991 in a 2–2 draw in Switzerland during the Euro 92 qualifiers. He was in Scotland's squad for the 1986 World Cup.