In 390 BC, as commander of Dionysius' fleet, he was dispatched to aid the Lucanians against the Thurians. Instead he affected a peace between the two parties, against the wishes of Dionysius. For this action, he was deprived of his command, which was given to his younger brother Thearides.
When Leptines married his own daughter to Philistus, the friend and supporter Dionysius I or Dionysius the Elder, the latter feared their conspiracy against him and exiled Leptines and Philistus. Together they travelled to Thurii, where due to Leptines' earlier conduct, they received a warm welcome.
Leptines eventually reconciled his differences with Dionysius, who gave him his daughter Dicaeosyne in marriage.
In about 375 BC, Leptines was killed in the Battle of Cronium against the Carthaginians.