The isobaric specific heat capacity c(p) of 2,3,3,3-tetrafluoroprop-1-ene was measured in the gaseous state and the behavior was presented in c(p)-T and c(p)-p diagrams. A total of 62 c(p) data were obtained for temperatures (T) in the range of 289 to 353 K and for pressures (p) of 0.3 to 2.2 MPa with a flow calorimeter. Some of them were obtained in the immediate neighborhood of the saturation regime. The estimated expanded uncertainties (k = 2) of the temperature measurements U(T) and the pressure measurements U(p) is to be less than 33 mK and 12 kPa, respectively. That for c(p) measurements U-c(c(p)) are calculated to be from 10 to 60 J.kg(-1).K-1. Also, two published equations of state were evaluated with the c(p) measurements. Using the measurements and evaluated data, several isotherms and the saturation of 2,3,3,3-tetrafluoroprop-1-ene in the gas phase were presented in the c(p)-p diagram.