Wachtmeister was born at Wanås Castle, Sweden, the son of cabinet chamberlain, count Gustaf Wachtmeister and his wife Margaretha (née Trolle). He passed "studentexamen" at Sigtunaskolan Humanistiska Läroverket in 1941 and received as Candidate of Law degree from Stockholm University College in 1946 and was hired by the Ministry for Foreign Affairs as an attaché the same year. Wachtmeister served in Vienna in 1947, Madrid in 1949, Lisbon in 1950 and the Foreign Ministry in Stockholm in 1950. He became second secretary at the Foreign Ministry in 1952 and was appointed embassy secretary in Moscow in 1955. Wachtmeister was first secretary there in 1956. Wachtmeister's first prominent role within the diplomatic community was as U.N. General Secretary Dag Hammarskjöld's personal assistant from 1958 to 1961. He was appointed Director ("Byråchef") in 1962 and he was Deputy Head of the Political Department at the Foreign Ministry in Stockholm from 1965 to 1966. Wachtmeister was ambassador in Algiers from 1966 to 1967 and served as Director ("Utrikesråd") and Head of the Political Department at the Foreign Ministry from 1968 to 1974.