Wear gloves, an N95 mask, and eye protection
Open windows and improve ventilation
Fix the moisture source first
Remove and discard any wet, porous materials that are moldy and cannot be cleaned
Mix warm water with mild detergent
Scrub the moldy wall surface with a sponge or brush
Wipe the area with clean water
Dry the wall completely with fans or a dehumidifier
Use a mold-killing cleaner if needed, following the label instructions
Do not mix bleach with ammonia or other cleaners
Repaint only after the wall is fully dry and mold-free
Clean and dry nearby surfaces and tools
Dispose of contaminated cleaning materials in sealed bags
Call a professional if the mold covers a large area or keeps returning