A series of non-equiatomic Al-Co-Cr-Fe-Nb-Ni high-entropy alloys, with varying levels of Al, Co, Nb and Fe, were investigated in an effort to study the formation and stability of precipitate phases. Elevated levels of Nb and Co were observed to promote the formation of undesirable phases, identified as Laves, NiAl, Ni3Nb, among others. Those formed either during solidification and remained undissolved during homogenization or upon high-temperature aging. High levels of Fe considerably increased the Laves phase solvus temperature up to incipient melting. Lowering the content of Nb, Co or Fe prevented the formation of these intermetallic phases and resulted in the formation of fine γʹ precipitates similar to Ni-based superalloys. Various aging treatments were studied to observe the precipitation and stability of the different phases. Results from the microstructural characterization and thermo-dynamic predictions from different databases on these high-entropy alloys will be presented.