Disclosed herein is a rural mailbox indicator and security lock including an elongated rod designed to be moved between three positions, a first position indicating that the box is unlocked but no mail is there for pick-up, a second position wherein the box is open and mail is in the box to be picked up and a third position indicating that the box is securely locked against unauthorized entry. The elongated rod is rotatably mounted on a cam which is adjacent a locking mechanism, with the cam having a cut out portion designed to receive a latch of the locking mechanism in the third mentioned position of the elongated rod described above, with the cam further including an arcuate rim designed to interengage with a catch formed on the mail box door so that in the position of the elongated rod corresponding to locked condition, the door is prevented from being opened until the locking mechanism is released by a key.