How to Clean Mold and Mildew From Caulk in a Few Simple Steps

Mold and mildew creeping along caulk lines may be a common sight in bathrooms and kitchens—but that doesn’t mean you have to live with these dark spots marking up the seams around your tubs, sinks, and backsplashes. When treated early, mold and mildew on grout are often removable using gentle, effective methods and a little expert know-how. 

Safety First

Before you begin, it’s important to protect both yourself and your space. "Start with safety first," says home maintenance expert Angi Hicks, co-founder of Angi. "Always work in a well-ventilated space and wear gloves and a mask, as both mold spores and cleaning agents can pose health risks if you’re not properly protected."

Open windows, turn on exhaust fans, and gather your supplies before starting to avoid cross-contamination while cleaning.

How to Clean Moldy Caulk, Step by Step

According to our experts, simpler solutions are not only safer—they’re often more effective. "Avoid harsh chemicals,” says Hicks. "Bleach and ammonia can harm both caulk and surrounding surfaces, so stick to gentler, safer solutions whenever possible."

Opt for natural cleansers and follow the steps below. According to Hicks, "If the caulk is still intact and the mold hasn’t penetrated deeply, a thorough cleaning with safe solutions like vinegar or hydrogen peroxide should do the trick."

1. Ventilate the area and put on gloves and a mask.
2. For less stubborn spots or routine maintenance cleaning, Hick recommends using white vinegar. "It’s non-toxic, kills mold effectively, and is safe for most surfaces, making it a go-to solution for routine maintenance," she says. Add it to a spray bottle and then spritz the area until fully covered. 
3. Allow the vinegar to sit for 15 to 30 minutes to break down mold spores.
4. Next, create a paste by combining baking soda and warm water. Apply it to the caulk and scrub gently with an old toothbrush. "Use baking soda for gentle scrubbing," says Hicks. "It helps lift mold and absorb moisture while protecting caulk and finishes from scratches or damage."
5. Rinse thoroughly.
6. Optional: "Turn to hydrogen peroxide for tougher spots," says Hicks. "A 3 percent solution can break down stubborn mold without damaging surrounding areas, providing a safe but powerful alternative." Apply and allow to sit for 15 to 30 minutes to allow the solution to penetrate. Then, gently scrub with a soft-bristle cleaning brush or old toothbrush.
7. Rinse and wipe clean, removing any residue or lingering cleaning solution. Dry well to prevent moisture from lingering.

Address the Root Cause

"The most effective long-term strategy isn’t just cleaning," explains Joshua Miller, president of Rainbow Restoration. "It’s fixing the source of moisture and managing humidity levels in the room to prevent regrowth."

To truly prevent mold from returning, you’ll need to tackle this underlying issue. "To protect your surfaces permanently, focus on improving airflow with exhaust fans or dehumidifiers," says Miller. "Keeping the surface dry is the best 'DIY method' to ensure you don't have to use harsh scrubbers that could scratch or damage delicate tile and grout."

Running an exhaust fan during and after showers, addressing leaks promptly, and regularly wiping down wet surfaces can all make a significant difference. Even a quick pass with a dry microfiber cloth after showering can help prevent moisture—and later, mildew and mold— from settling into the caulk.

When It's Time to Replace Your Caulk

Not all moldy or mildewed caulk can be saved. If the caulk is smooth, flexible, and firmly adhered, you’re likely dealing with a surface issue. Following the cleaning steps above can likely restore its appearance. "However, because caulk is porous, mold often grows behind or through it," warns Miller. "You should replace it entirely if the mold keeps returning despite cleaning, or if the caulk is cracked, peeling, or pulling away from the surface."

"Replace it if the caulk is compromised," agrees Hicks. "Cracking, peeling, shrinking, or persistent staining are signs the seal is no longer effective. At that point, replacement is the better option." Replacing caulk may feel like a bigger project, but it’s often the only way to fully eliminate deeply embedded mold and restore a proper seal against moisture. "Once the old caulk is removed, ensure the gap is completely dry and the underlying leak or humidity issue is addressed before resealing," Miller adds.

Less moisture, less mildew, less scrubbing.