Friedrich Casimir was born in Bouxwiller (German: Buchsweiler), the residence of the county of Hanau-Lichtenberg, as the son of Count Philipp Wolfgang (1595–1641) and his wife, Countess Johanna of Oettingen-Oettingen (1602–1639).

He visited countries that were not affected by the Thirty Years' War: France, Spain, Italy, England and the Netherlands.

Initially, the committee consisted of Johann Ernst of Hanau-Münzenberg and Baron Georg II of Fleckenstein-Dagstuhl, who was a great-grandson of Count Philipp IV of Hanau-Lichtenberg.

When Friedrich Casimir took office in Hanau-Münzenberg, the county was financially in a precarious situation, due to the Thirty Years' War.

Friedrich Casimir had to travel through enemy territory in disguise, accompanied by his guardian Georg II of Fleckenstein-Dagstuhl and a small security detail.

Several liege lords of Hanau-Münzenberg, in particular the Archdiocese of Mainz, but also the Electorate of Saxony, Hesse-Darmstadt, the Bishopric of Würzburg and the Imperial Abbey of Fulda held that the family relationship between Friedrich Casimir and Johann Ernst was too distant and that Johann Ernst therefore had no male heir, so the fief was completed and should be terminated.

In return, Friedrich Casimir signed a treaty of inheritance, promising that if Hanau-Münzenberg were to die out in the male line, the country would fall to Hesse-Kassel.

Its leadership was composed of wealthy merchants and traders who took advantage of the weak position of the new count to negotiate favourable conditions, in particular, they demanded guarantees that the religious status quo would be maintained.

After ten days of negotiating, Georg of Fleckenstein-Dagstuhl gave this guarantee, so that Friedrich Casimir could finally accept his inheritance.

Back then, Philipp Ludwig II had been able to decide the denomination for himself and his subjects under the principle of Cuius regio, eius religio, Friedrich Casimir not only had to allow the Calvinists to retain their religion; initially Friedrich Casimir could only hold Lutheran services for himself and his court in the chapel in the City Palace.

The political landscape in which Friedrich Casimir had to operate, remained marked by uncertainty, even after the Peace of Westphalia.

The part of Hanau-Lichtenberg on the left bank of the Rhine had been separated from the Holy Roman Empire by the Peace of Westphalia and were placed under the sovereignty of the French crown.

After the Peace of Nijmegen of 1678 and a verdict of the Chamber of Reunion in 1681, Friedrich Casimir had to pay homage to the French king for these areas.

Among his advisors were the doctor and Alchemist Friedrich Kretschmar, a vagabond and princely advisor with a dubious reputation, Swedish councillor Bengt Skytte, a self-styled philosopher, Johann Joachim Becher, a doctor and economic theorist, Landgrave Georg Christian, a soldier and diplomat, and the author Johann Michael Moscherosch.

During Friedrich Casimir's reign, one of the first faience manufacturing plants in Germany was founded by Daniel Behaghel and Jacob van der Walle, using a countly privilege issued on 5 March 1661; it would operate successfully until the early 19th century.

Several treaties were concluded with the Archdiocese of Mainz and the Bishopric of Würzburg, which were both administered by Johann Philipp von Schönborn in apersonal union, on the one hand resolving disputes which had arisen during the Thirty Years' War, on the other hand exchanging territories in order to make both countries more convex.

To compensate for the loss of population of the war, he promoted immigration of Swiss people from the Bernese Oberland into the county of Hanau-Lichtenberg.

The high point of his fantastic projects was the foundation of the Hanauish Indies, a colony that would arise on the Orinoco river on the north coast of South America.

He was also alleged to try to transfer the district of Dorheim to his own Landgraviate, including the salt mine of Bad Nauheim, which was vital for the economy of Hanau.

His brother, Johann Philipp of Hanau-Lichtenberg staged a coup in November 1669 and seized power while Friedrich Casimir was absent.

Friedrich Casimir's councillor were dismissed and a new government was installed, led by President of the Chamber Johann Georg Seyfried, who was later ennobled as Baron von Edelsheim.