A utility knife comprises a blade carrier movable between retracted, extended and positions. A latch is movable with the blade carrier for locking the blade carrier in position. The blade carrier comprises a locking tab movable between a first position where the locking tab is engaged with the blade and a second position where the locking tab is released from the blade. An actuator moves the locking tab from the first position to the second position when the blade carrier is in the intermediate position and the actuator is moved to the unlocked position. The latch is engageable with a holder when the blade carrier is in the intermediate position. A retention member holds the blade on the plate where the retention member cannot be inserted into a notch on the blade. A blade guide guides the blade between the retention member and the plate.