Replant the cactus if it was disrupted when it broke. Ensure the cactus is firmly secured in the soil.
Spray the broken areas of the cactus with a solution of 8 parts water to 1 part bleach. This disinfects the wounds and helps them heal.
Cover the cactus with a 30-percent blackout shade cloth during the summer months until the wounds have healed. The long days under the hot sun will damage the cactus if the broken sections haven't closed themselves up yet. Keep the shade off on cooler days.
Water the cactus once or twice a month on a slow drip for no longer than three hours. Ensure the dirt is completely dry before watering. If it isn't, hold off until it is so the cactus doesn't drown.