He was the only son of Bolesław II, Duke of Cieszyn, by his wife Anna, daughter of Ivan Vladimirovich, Prince of Bielsk.
However, Casimir II couldn't take the government over the other half of Głogów, then under the rule of Margareta of Celje, widow of his uncle Władysław as her dower.
Despite the formal abandonment of his pretensions in Lower Silesia, Casimir II didn't change his ambitions, and in 1480 he obtained Pszczyna after his marriage with Johanna, daughter of Wiktoryn of Poděbrady, Duke of Opava (although in practice he could take formal possession of this land only in 1498), who was supposedly to be a great help to him in his plans to regain Głogów, then under the rule of Jan II.
Another defeat, this time at the Battle of Góra, forced Casimir II to accept the definitely resignation of the disputed territory on 7 June 1481.
However, when Sigismund inherited the Polish crown in 1506, after the death of his brother Alexander Jagiellon, the dignity of Starost returned to Casimir II.
However, his rule as Starost general wasn't count with great support in Silesia, especially with the Church, whose opposition was made clear in 1501, when the Chapter refused the candidacy of Casimir II's eldest son Frederick as new Bishop of Wrocław.
Duke Jan II, after hearing the news of his brother's execution, began to prepare a brutally retaliatory expedition against Cieszyn.
However, the diplomatic actions of King Władysław II Jagiellon prevented the war between both dukes, with disastrous consequences to Silesia.
[citation needed] The Duke of Cieszyn's political importance reached his apogee in 1512, when King Sigismund I the Old married with Casimir II's niece Barbara Zápolya (daughter of his cousin Hedwig).
In 1517, during transitional financial difficulties, Casimir II decided to sell the town of Pszczyna to the Hungarian magnate Alexis Thurzo for 40,000 guilders.
The salary of Casimir II as Starost General (1,200 guilders a year), and the incomes derived from the towns near Kraków allowed him to buy the cities of Mistek and Friedland from the Bishop of Olomouc in 1527.