By means of molecular dynamics simulation, the process of the microphase separation in the melts of diblock helix–coil copolymers comprising a flexible and a helical block was studied. The resulting microstructures were examined, and the spatial distribution of the blocks and molecular packing were investigated. The phase diagram was built in terms of the fraction of the helical block and the incompatibility parameter of the blocks. The comparison of the diagrams for helix–coil and the classic coil–coil copolymer blends was carried out. It was shown that the total region where the ordering into distinctive microstructures takes place is similar for both diagrams. But for the helix–coil copolymers the area of the cylinders splits into the region of those with circular and elliptical cross-sections; the bicontinuous phase area is much wider; in the lamellar phases, the helical blocks were oriented precisely perpendicular to the lamellar interface, forming a cohesive interlocked structure of densely packed helices.