This paper presents the behavior of the interfacial bond between an innovative FRP fibre and cement mortar under time-dependent loading. Two types of FRP fibres—GFRP and CFRP were investigated. Particularly, the fibre pullout response under quasi-static loading is compared with the response under dynamic loading. To gauge the long term behavior of cracked fibre reinforced composites, fibre relaxation tests were conducted in which initial strain was imparted and sustained, and the relaxation of the composite in terms of drop in load over time period was monitored at room temperature as well as at 50 °C. FRP fibres were found to be to some extent sensitive to loading rate, with an increase in the range of 30–50% in the peak load under dynamic loading. The GFRP fibres itself depicted higher strengths under dynamic loading rate. Under a sustained fibre slip, FRP fibres showed a lower relaxation at both room temperature and at 50 °C compared to commercially available steel and polypropylene fibres. There was also no conclusive change in pullout response in specimen subjected to sustained strains compared to reference.