The self-assembly behavior of AB/AC amphiphilic diblock copolymer mixtures in dilute solution was studied by a real-space-implemented self-consistent field theory in three dimensions. The AB and AC copolymers have a common hydrophobic block A but different hydrophilic blocks B and C. Two cases were studied: one in which copolymers AB and AC have same hydrophobic and hydrophilic block lengths and one in which copolymers AB and AC have different hydrophobic and hydrophilic block lengths. It was found that the two copolymers can cooperatively self-assemble into hybrid aggregates. The morphologies of the formed aggregates were found to be dependent on the mixture ratio and the interaction between the B and C blocks. For the AB/AC copolymers with different hydrophobic and hydrophilic lengths, chain segregation was found in the formed hybrid aggregates. Based on the obtained calculation results, phase diagrams as functions of the mixture ratio and interaction between the B and C blocks were constructed.