ρ Pup is a δ Scuti type pulsator with relatively low amplitude (ΔV∼0.m09). Analysis of the data from different sources, using the Fourier Transform method, establishes ρ Pup as a monoperiodic pulsator. Using the classical O-C method, it is found that the pulsation of this star can be well described by means of a linear ephemeris with a period of P=0.d140881372 over more than eighty years. The nature of radial or nonradial pulsation is discussed on the basis on the derived phase shifts and amplitude ratios between different colours. The results indicate that ρ Pup is a radial pulsator.