This paper presents comparative study between fractional-order PI (FOPI) and PI controller for steam temperature control. Both controllers were tuned using Ziegler-Nichols tuning rules based on identified steam temperature model in FOPDT structure. Simulation studies show the feasibility of using the original Ziegler-Nichols rules in producing significant improvement of FOPI over the PI with the same control parameter. However, overall performances of FOPI are dependent on the fractional-order and minor modification on its low-frequency response is required. This study also proposed a practical solution for the problem by introducing an auxiliary function called as an error filter. Overall performances of both controllers were validated with experimental results that show good agreement with simulations.