Morsztyn was born 24 July 1621 at Wiśnicz, near Kraków, into a wealthy Calvinist family of coat-of-arms "Leliwa". He studied at Leiden University and, with his brother, traveled extensively in Italy and France. After returning to Poland, he became a retainer of the magnate Lubomirski family, and through them became attached to the royal court. He was a deputy to the Sejms of 1648, 1650, 1653, 1658 and 1659. He served on numerous Sejm commissions for diplomatic, legal and fiscal matters. He took part in diplomatic missions to Hungary (1653), Sweden (1655) and Austria (1656).