This paper presents speed of sound measurements of liquid trans-1-chloro-3,3,3-trifluoropropene (R1233zd(E)) along six isotherms over the temperature range from (273.15 to 353.15) K for pressures up to 35 MPa by means of the double pulse-echo method. The expanded uncertainty of the speed of sound measurements at a confidence level of 95% is 0.1%. The experimental results were compared with predictions from the state-of-the-art Fundamental Helmholtz Energy equation of state [Mondejar, M.E.; McLinden, M.O.; Lemmon, E.W., Thermodynamic Properties of trans-1-Chloro-3,3,3-trifluoropropene (R1233zd(E)): Vapor Pressure, (p,rho,T) Behavior, and Speed of Sound Measurements, and Equation of State].