The present invention relates to a catalyst composition for the oligomerization of ethylene comprising at least one transition metal bisphenolate compound and at least one cocatalyst. The transition metal bisphenolate is a zirconium bisphenolate. The invention also relates to a process for the oligomerization of ethylene in the presence of the catalyst composition according to the invention. The process results in a high yield of C-Clinear alpha-olefin and C-Clinear alpha-olefin.