Most of the work performed on the use of water/oil emulsions in diesel engines showed that increasing the water content in the emulsified fuel was effective in reducing NOX and soot emissions. Unfortunately, the increase in water content in the emulsified fuel also increases the ignition delay and may cause diesel knock. One way to reduce the ignition delay is to increase the air charge temperature. In this study, the effect of increasing the air charge temperature on ignition delay, performance and exhaust emissions was investigated. The experiments were conducted on a CLR diesel engine using baseline diesel fuel #2 and stabilized macroemulsions containing 15 percent, 30 percent and 45 percent water by volume. The air charge temperature was varied from ambient to 75°C and 150°C. The performance results showed that under same operating conditions, when neat diesel fuel was used, increasing the air charge temperature caused the BSFC to increase. When emulsified fuel was used, especially with low water content, increasing the air charge temperature improved the BSFC at low loads and increased it at high loads. The ignition delay was also effectively reduced with the increase of air charge temperature. The emission results indicated that under the same operating conditions, NOx and soot emissions increased with the increase of air charge temperature, while CO and UHC emissions, in general, were slightly reduced at low loads and increased at high loads.