A fuel supply control apparatus for an engine includes an alcohol concentration detector and an engine temperature detector. The apparatus increases an amount of fuel supplied to the engine as the detected alcohol concentration becomes higher. The apparatus increases the amount of fuel as the engine temperature becomes lower and as the alcohol concentration becomes higher. The apparatus feed-back corrects the amount of fuel by using a correction value such that an actual air-fuel ratio becomes a theoretical air fuel ratio. The apparatus determines that water is mixed with fuel when the correction value during a cold operational state indicates leaner than the lean value of the correction value used during a warm operational state. The apparatus reduces the increased amount of fuel when water is mixed with fuel.