Alloying with reactive elements, such as Ti, enhances the ability of Cu melts to wet graphite. However, our understanding of the reactive wetting and kinetic mechanisms of the Cu–aTi/C system at high temperatures is still controversial. The reactive spontaneous infiltration (RSI) of Cu–aTi alloys (a = 17, 34, 68 at. %) into porous graphite and the spreading wetting (SW) on dense pyrolytic graphite were examined to elucidate the effect of the Ti content on the RSI and SW mechanisms and kinetics. The reactive wetting behaviors were investigated using a modified sessile drop method, and the interfacial microstructures, elemental distributions, and phase compositions of samples were characterized using instrumental techniques. With increasing Ti content, TiCx became depleted in carbon and experienced a morphology change. The mechanisms of RSI and SW were controlled by the synergistic effects of Ti content and TiCx. By fitting the time-dependent variation of the relevant parameters (contact angle, spreading radius, infiltration volume, and infiltration depth) for the two substrates at the same Cu–aTi alloy content using reaction- and diffusion-limited models in the reactive wetting system, we found that the kinetics of these two processes were controlled by similar mechanisms.