This paper reports visualization results of two-phase flow of R1233zd(E) and R1336mzz(Z) in a 24-port microchannel tube. The tube has an averaged hydraulic diameter of 0.643 mm. Mass flux is in the range from 50 to 200 kg-m-2s-1. Flow patterns are classified as plug/slug, transitional, and annular flow. In plug/slug flow, a clear interface between liquid slug and vapor plug is observed. In transitional flow, the interface between vapor plug and liquid slug is broken and becomes a thick liquid ring and vapor bridge. In annular flow, only liquid film is observed in the tube. Both mass flux and vapor density strong affect the flow pattern because they affect the flow velocity. The results are compared to other fluids tested on the same facility: R32, R134a, R1234ze(E), and R1234yf. R134a, R1234ze(E), and R1234yf have similar flow patterns at the same condition. Both R1233zd(E) and R1336mzz(Z) also have similar flow patterns because they have similar properties.