You'll know it's time to repot your monstera when roots are growing out of the holes in the bottom of the pot or appear to fill the soil surface. You may also notice that your plant seems to dry out a day or two after watering. These are signs that the plant is rootbound and could benefit from repotting in a larger container.
Other signs that it's time to repot a monstera plant include overgrown foliage that threatens to tip over the plant and stunted growth or a dull appearance. Even if your monstera doesn't seem to be outgrowing its pot, it's a good idea to repot it with fresh soil every two years or so.
Prep the new pot. Fill the new pot about one-third full with fresh potting soil. Skip adding rocks or shards of ceramic to the bottom of the pot, as these can inhibit proper drainage.

Carefully tip the plant out of its current pot and lift the container away from the root ball. Be sure to support the moss pole if your plant has one, to keep it attached to any aerial roots. 

Using your fingers, gently massage the root ball to loosen the roots and remove old soil. Avoid breaking or damaging any roots. Inspect the root ball for any signs of rot or damage—they should be firm and white. Use clean, sharp pruners to remove any soft, black roots.

Plant the Monstera in the New Pot. Pick up the monstera with one hand on the root ball and one at the base of the plant, then place it into the new pot. Fill in the area around the root ball with fresh soil. Adjust to make sure the soil level is the same in the new pot. Leave about one inch of space between the top of the soil and the rim of the pot.

If your monstera has grown aerial roots, it’s a good idea to train the roots back toward the soil after repotting. They'll help support the plant and putting them back in the soil can help the plant take up additional nutrients.

Water the monstera well—enough that water runs out of the holes in the bottom of the pot. Let the soil drain fully before placing the plant back into a cache pot or drip tray to keep the plant from sitting in water.

After watering, put your monstera back in its usual location. This will help the plant adjust and keep it from going into shock. Avoid fertilizing for at least six weeks after repotting to avoid damaging new roots. If you've repotted during fall or winter, you can wait until the following spring to start fertilizing again.