The grout in my shower is moldy and gross. What is the best grout cleaner to make it look new again?

When dealing with mold and gross buildup in shower grout, the "best" cleaner depends on whether you are fighting surface mold/mildew or deep, stained grime.

Top-rated grout cleaners and heavy-duty options include:

• For Heavy-Duty Restoration & White Grout: ZEP Grout Cleaner and Brightener (available via The Spruce ) is an acid-based powerhouse that eats through deep-set dirt and discoloration, making dingy grout look brand new. (Note: Do not use on natural stone like marble or granite).
• For Mold & Mildew Stains: Clorox Clean-Up Cleaner + Bleach or Tilex Mold & Mildew Remover excel at actively killing organic mold and whitening dark, mildewed lines. As The New York Times' Wirecutter notes, a bleach-based gel toilet bowl cleaner also clings nicely to vertical shower walls and lifts stains surprisingly well.
• For a Plant-Based/Gentler Approach: Mrs. Meyer's Clean Day Tub and Tile (tested by The Spruce ) is great if you want to avoid harsh chemical fumes, though it requires a bit more elbow grease on heavily stained grout.

How to Get the Best Results:

1. Scrub with the right tool: Spray your cleaner of choice and let it sit for 5 5 5 to 10 10 1 0 minutes to break down the roots of the mold. Use a stiff-bristled brush (like an OXO Grout Brush ) rather than a soft sponge to agitate the cleaner into the pores of the grout.
2. Rinse thoroughly: Wash away the loosened grime with warm water.
3. Seal it (Crucial step): Once the grout is completely dry, apply a liquid grout sealer. This fills the microscopic pores so mold, mildew, and soap scum can't easily root themselves there again.

If you'd like, tell me:

• Is your tile ceramic/porcelain or natural stone (like marble)?
• Is the grout colored or originally white?

I can give you a precise product recommendation that won't accidentally damage your specific materials.

For moldy shower grout, I’d go with a bleach-based mold/mildew remover, rather than a generic grout cleaner. Bleach is particularly effective at removing the black/gray discoloration that makes grout look awful.Clorox™+1

• Clorox Plus Tilex Mold and Mildew Remover - $6.98 (The Home Depot)

My pick: Clorox Plus Tilex Mold & Mildew Remover

It’s specifically made for bathroom mold and mildew, contains bleach, and is designed to remove the stains without requiring much scrubbing. Clorox says it can be used on grout and glazed tile and claims it kills 99.9% of mold and mildew.Clorox™

For really nasty grout:

1. Ventilate the bathroom well and put on gloves.
2. Spray the grout thoroughly.
3. Let it remain wet for about 5–10 minutes according to the product directions.
4. Scrub stubborn areas with a stiff nylon grout brush.
5. Rinse extremely well and let everything dry completely.
6. Repeat if necessary.

• Clorox Plus Tilex Mold & Mildew Remover - $6.98 (The Home Depot)
• Zep Home Pro Mold & Mildew Stain Eraser - $4.92 (Walmart)
• RMR-86 Instant Mold & Mildew Stain Remover - $8.97 (Walmart)

Important: Never mix bleach with vinegar, ammonia, or other cleaners—the resulting fumes can be dangerous. Also, bleach isn't appropriate for every tile/stone surface; avoid it on marble and other porous/bleach-sensitive materials.Clorox™+1

If the grout is black throughout rather than just surface-stained, or the blackness is actually in the silicone caulk, cleaning may not make it look new—you may need to remove and replace the caulk.

If you tell me whether your shower is white ceramic tile, porcelain, natural stone, or something else, I can tell you exactly what I'd use and how I'd clean it without damaging the grout.

When shower grout gets dark, slimy, or stained with mold, standard all-purpose bathroom sprays usually won't cut it. Because grout is porous, mold roots dig right into it.

To make it look brand new again, the "best" cleaner depends on whether you are tackling active mold stains or deep-set dirt and soap scum:

• For Mold and Mildew Stains (The Whitening/Disinfecting Route): A chlorine bleach-based spray like Clorox Plus Tilex Mold and Mildew Remover or Ecolab Mold and Mildew Stain Remover works wonders. Bleach kills the active fungi and instantly bleaches out the dark, unsightly mold staining without requiring aggressive scrubbing. Just spray, let it sit for a few minutes to foam and penetrate, and rinse. (Caution: Do not mix bleach with other cleaners like vinegar or ammonia). [1][2]
• For Deep-Set Grime and Soap Scum (The Heavy-Duty Non-Bleach Route): If the discoloration is a mix of body oils, hard water, and dirt rather than pure black mold, a specialized alkaline or peroxide cleaner like [Black Diamond Stoneworks Ultimate Grout Cleaner ](https://bdstoneworks.com/products/ultimate-grout-cleaner?variant=47941719228570&country=US&currency=USD&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&srsltid=AU7gw4USN6zsTdOUqStCHndaRp99W7i3mwTZguVprke_JnFZyT7E-Zr321M) or Granite Gold Grout Cleaner safely breaks down embedded grease and lifts stains without harsh acids.[1][2]
• The Secret Weapon (The Tool): No matter what chemical you choose, the cleaner alone won’t do all the work. Pair it with a stiff-bristled grout brush (or an old electric toothbrush) to physically agitate the cleaner into the porous lines.

If the grout is permanently stained beyond what cleaning can fix, your ultimate last resort to make it look brand new is applying a grout pen or colorant sealer , which paints over the old dingy lines with a fresh, stain-resistant barrier.

If you want to narrow this down, let me know:

• Is your tile made of ceramic, porcelain, or natural stone (like marble)?
• Is the discoloration black/pink mold , or is it yellowed/stained from hard water and age?

I can give you the exact safe cleaner and step-by-step game plan.

If your goal is “make the grout look new again”, I’d go with a bleach-based mold/mildew remover, rather than a general-purpose grout cleaner.

• Zep Mold & Mildew Stain Eraser - $4.99 (Target)
• RMR-86 Instant Mold & Mildew Stain Remover - $9.19 (Target)
• Clorox Plus Tilex Mold & Mildew Remover - $5.79 (Target)
• Zep Mold & Mildew Stain Remover Gel - $7.98 (Lowe's)

My pick: Zep Mold & Mildew Stain Eraser

It’s inexpensive, specifically designed for mold/mildew stains on grout and tile, and the bleach-based formula is particularly good at restoring white grout.

For really black, nasty grout, I'd step up to RMR-86. It's formulated for stubborn mold/mildew staining and is designed to work with little or no scrubbing.

How I'd tackle your shower

1. Ventilate the bathroom and put on gloves.
2. Spray the moldy grout thoroughly.
3. Let it sit according to the product's label directions.
4. Scrub stubborn areas with a stiff nylon grout brush.
5. Rinse extremely well.
6. Repeat once if necessary.

Important: Never mix bleach-based cleaners with vinegar, ammonia, acids, or other cleaners. Also, if the grout is permanently darkened because mold has penetrated deeply—or if the caulk/silicone is black underneath—it may not clean back to “new.” In that case, replacing the caulk or regrouting can give you the genuinely new-looking result.

If you tell me whether your grout is white, gray, or colored, and whether the mold is black spots vs. an overall dingy discoloration, I can tell you exactly which cleaner I'd use and how I'd attack it.