We report the first direct measurements of ultrafast electronic relaxation dynamics in PbI2 colloidal nanoparticles using femtosecond transient absorption spectroscopy. The PbI2 nanoparticles were prepared using colloidal chemistry methods in different solvents, including ethanol, 2-propanol, 1-butanol, water, and acetonitrile, as well as in poly(vinyl alcohol) (PVA) matrix. The particle sizes were determined using low- and high-resolution transmission electron microscopy and atomic force microscopy, which provided direct evidence of photodegradation of the nanoparticles. The ground state electronic absorption spectra of aged PbI2 nanoparticles in acetonitrile and alcohol solvents showed two major peaks near 360 and 292 nm, which slightly blue shift with decreasing size. In aqueous solution containing PVA a new sharp excitonic peak appeared at 414 nm, indicative of nanoparticle formation. With excitation at 390 nm and probing in the visible to near-infrared region, the electronic relaxation dynamics in Pb...