Yellow leaves on a peace lily, diagnosed.

It's overwatering. Probably. Here's how to be sure — and the four other suspects.

1. Overwatering (most likely)

If multiple lower leaves are yellow at once and the soil feels constantly damp, you've overwatered. Roots can't breathe in soggy soil; they suffocate, and the plant abandons leaves to conserve resources.

Fix: stop watering. Let the top two inches dry out before the next drink. If the plant doesn't recover within two weeks, suspect root rot and unpot to inspect.

The fastest clue is the pot, not the leaf. A heavy pot, wet drainage holes, a sour smell, or a saucer that keeps collecting water all point to a moisture problem. If the pot has no drainage hole, move the plant to a draining pot as soon as possible.

2. Natural aging

One yellow leaf, on the outside, on an otherwise happy plant? That's just a leaf retiring. Snip it at the base.

Natural aging usually affects the oldest outer leaf one at a time. The rest of the plant should look firm, upright, and green. If several leaves yellow together, or new leaves yellow first, treat it as a care problem.

3. Low light

Light-starved peace lilies will sacrifice their oldest leaves to feed the rest. Pale, slow-growing, never blooming → move closer to a window.

Low-light yellowing is gradual. You may also see long petioles, smaller leaves, and soil that stays wet for too many days because the plant is not using water quickly. Move the plant one step brighter, then watch the next two leaves rather than expecting yellow leaves to recover.

4. Mineral / fluoride burn

Yellowing that starts at the tip and creeps inward, often with a brown tip first, is tap-water damage. Switch to rainwater or filtered.

If you also see white crust on the soil or pot rim, flush the soil with plenty of room-temperature water and let it drain fully. Filtered, distilled, or rainwater can reduce new tip burn, but old yellowed tissue will stay yellow.

5. Cold draft

Yellow patches that turn black overnight? Check for an AC vent or a leaky window.

What to do today

1. Feel the soil two inches down and lift the pot to judge weight.
2. Check the leaf pattern: one old leaf, many lower leaves, tips first, or black patches.
3. Empty any saucer water and pause watering if the mix is damp.
4. Move the plant to bright indirect light, away from cold glass and vents.
5. Remove fully yellow leaves at the base so the plant can redirect energy.

Will yellow leaves turn green again?

No. Once a peace lily leaf turns fully yellow, it will not green back up. Recovery shows through new leaves, firmer stems, and the yellowing pattern stopping. This is why diagnosis matters: the goal is not to save the yellow leaf, but to stop the next one from yellowing.

When to inspect roots

Unpot the plant if yellowing is paired with drooping in wet soil, a sour smell, black mushy stems, or soil that remains wet for more than a week. A quick root check is less risky than letting a rotting plant sit. Healthy roots are firm and pale; rotted roots are brown, soft, and may slide apart when touched.

How to prevent the next yellow leaf

Give the plant a stable routine: bright indirect light, a draining pot, and watering based on the soil rather than a calendar. Empty saucers, avoid cold drafts, and feed lightly only during active growth. Most repeated yellowing comes from one of those basics being off by a little for too long.