This paper aims to address the transient phenomenon in pulsed-laser-induced heating for nanoshell-based hyperthermia. Within the framework of dual phase lag model, the transient temperature with the relaxation behavior involved was compared with that based on Fourier's law. The temporal variation of temperature is investigated under the irradiation of pulsed laser, as well as continuous-wave (CW) laser. A semianalytical solution of 1-D nonhomogenous dual phase lag equation in spherical coordinates is presented. The results show that the transient temperature with relaxation behavior considered is generally higher than that predicted by a classical diffusion model. The magnitude of difference depends on pulsewidth, duty cycle, and repetition rate. The maximal transient temperature is as high as 350 times the steady-state temperature in a CW case. The biological effect caused by the overheating in a short period needs to be studied further.