Leijonhufvud was one of Crown prince Gustav's (III) cavaliers, a civil servant and a lord marshal of Sweden.
[1] Leijonhufvud became a student in Uppsala in 1730, extra ordinary chancellor in the chancellery in 1734 and a volunteer at the Life Guards in 1737.
Leijonhufvud was a cavalier to Crown Prince Gustav 1756–1762, was promoted in 1757 to major and in 1763 to lieutenant colonel before his resignation in 1766.
[1] Leijonhufvud became a member (number 1) and founder of the Royal Swedish Academy of Music in 1771 and was its first president.
[2] Leijonhufvud has authored Tanke-val i dag evangelier, uti vers, published in 1790, the year after his death.