Van de Kamp, who was born at Kampen in the Netherlands, studied at the University of Utrecht, obtaining his PhD in 1922. He emigrated to America in 1923 and, after appointments at the Lick Observatory (1924–25) and the University of Virginia (1923–24, 1925–37), became director of the Sproul Observatory and professor of astronomy at Swarthmore College, Pennsylvania. Following his retirement in 1972 he became research astronomer there.

In the 1960s van de Kamp found strong evidence for a new celestial phenomenon: planets orbiting stars other than the Sun. Since 1937 he had been studying the motion of Barnard's star, a nearby red star with a very large proper motion of 10.3 seconds of arc per year. By 1969 he was able to state that the star was oscillating very slightly in position about a straight line and that this wobbling motion was caused by an unseen companion. This companion was orbiting Barnard's star in about 25 years and was only about 1.5 times the mass of Jupiter. As this is too small a mass for a star, van de Kamp concluded that it was a planet. After further calculations he said that it was more likely that there were two planets, both of a similar mass to Jupiter, one orbiting in about 12 years and the other in 26 years.

This was not the only search for planets. In 1943 K. A. Strand claimed that he had detected a planetary body in the binary star 61 Cygni. His evidence was not as good as van de Kamp's however, although more recent observations indicate a planet about eight times the mass of Jupiter orbiting the brighter component of 61 Cygni in 4.8 years. There are other stars that have also shown perturbed motions from planet-sized companions.

The planets belong to stars that are relatively close. It is unlikely that this is merely coincidental and consequently van de Kamp and others concluded that planetary systems are likely to be widespread. Such a conclusion implies that some form of life may be present outside the solar system.