Aim: This in vitro study aimed to evaluate the effect of three curing times and intensities on the microtensile bond strength of bulk-fill resin composite and to assess the effect of thermocycling on the microtensile bond strength Subjects and Methods: A total of 18 freshly extracted caries-free human permanent molars were selected for this study. Teeth fixed in acrylic resin blocks were mounted in an automated diamond saw. Occlusal surfaces were flattened to the level of the dentino-enamel junction. A specially designed stainless steel holder was fabricated to hold and stabilize the acrylic block and the tooth during bonding and resin composite application. The bonding agent was applied to dentin with micro brush for 20 seconds with gentle agitation and light-cured for 20 seconds. Moreover bulk-fill resin composite was applied on each surface. The teeth were used to obtain ninety dentin rods. The rods were divided into three equal groups (n=30), according to light curing intensity and time (I): Group (I1): high intensity (2200 mw/cm2) for one second, Group (I2): high intensity (2200 mw/cm2) for 3 seconds, and (I3), low intensity (1200 mw/cm2) for 20 seconds. Each group was further divided into two subgroups according to thermocycling (C): either subjected (C1) or not (C0). Each subgroup was subdivided according to storage time (T): (T1) 24 hours, (T2) 3 months, and (T3) 6 months. Microtensile bond strength measurements were done using the universal testing machine.