[3] It was discovered by Swiss astronomer Philippe Loys de Chéseaux in 1745.

It is one of the brightest clusters not to be cataloged by Charles Messier or William Herschel, probably because it is so loose and coarse.

Age estimates for this cluster have ranged from 20 up to as high as 100 million years.

Comparison of the stellar lithium depletion with other clusters suggests it began to develop about 55 million years ago.

[7] There is evidence that IC 4665 is undergoing a collision with the older cluster Collinder 350, located about 4° away.