Abstract In this paper some new experimental data collected during R1233zd(E), a new hydrochlorofluoroolefin molecule, flow boiling inside a microfin tube having an inner diameter equal to 4.3 mm are reported. The tube was made of copper, set up in horizontal position and electrically heated from the bottom. The data, presented in terms of heat transfer coefficient and frictional pressure drop, were collected keeping the saturation temperature constant at about 30 °C, and modifying the heat flow rate, from 15 to 90 kW m−2 and the refrigerant mass flux, from 100 to 300 kg m−2 s−1. Moreover, some correlations available in open literature have been implemented and assessed against the experimental data. Particular attention was given to R1233zd(E) thermophysical properties because there are just few data available in literature and some researchers have highlighted the possibility that the related estimation uncertainties can compromise the reliability of models implementation and data comparisons.