Like his older cousin, future business partner and brother-in-law, Karl Erhart, Pfizer was born in Ludwigsburg, Kingdom of Württemberg[3] (now Germany).

[7] The couple had six children, five of whom survived to adulthood: Charles Jr (1860–1928), Gustavus (1861–1944), Emile (1864–1941), Helen Julia (born 1866, who married Sir Frederick Duncan, 2nd Baronet),[8] Alice (who married Baron Bachofen von Echt [de] of Austria), and Ann (1875–1876).

When Erhart died, in 1891, their partnership agreement came into effect, which stipulated that the surviving partner could buy the other's share of the company for half of its inventory value.

Pfizer promptly exercised this option, paying his partner's heirs $119,350 for Erhart's half of the business.

[3] Pfizer died on October 19, 1906[5] at his summer home, "Lindgate", in Newport, Rhode Island; his main residence was in Clinton Hill, Brooklyn.