The dual-fuel combustion strategy is a promising method to achieve the high-ratio utilization of isopropanol–butanol–ethanol (IBE) in diesel engines. However, how the diesel injection timing affects the combustion and emission characteristics of the diesel/IBE dual-fuel engine has been seldom systematically studied. In this regard, experiments were conducted on a diesel/IBE dual-fuel engine with the engine load fixed at 50% and the engine speed fixed at 1600 rpm, while the co-combustion ratio of IBE to diesel varied from 20.51% to 52.56%. The results show that both the peak in-cylinder pressure and maximum heat release rate increase as the diesel injection timing advances, resulting in the brake thermal efficiency of the diesel/IBE dual-fuel engine increasing. For emissions, CO emissions always decrease as the diesel injection timing advances, while HC emissions increase with the diesel injection timing either delayed or advanced. Furthermore, although the NO₂ emissions first increase and then decrease as the diesel injection timing advances, the NO emissions continue to increase, leading to an overall increase in NO_x emissions. However, whether the diesel injection timing is advanced or delayed, PN emissions are significantly reduced. That is to say, delaying the diesel injection timing can simultaneously reduce NO_x and PN emissions in a diesel/IBE dual-fuel engine.