Why mold cleanup usually falls on the landlord
In most cases, yes. A California landlord is generally responsible for fixing the moisture problem behind mold and arranging proper cleanup — especially when the cause is a leak or repair the landlord neglected.
Mold rarely appears on its own. It grows from water intrusion, plumbing leaks, roof damage, or poor ventilation. Because keeping the structure and plumbing in good repair is the landlord's duty, the mold that results is usually theirs to deal with too. Wiping the surface is not enough; the source of the water has to be fixed, or the mold comes right back.
There are exceptions. If a tenant clearly created the moisture — for example, by causing a flood and never reporting it — responsibility can shift. But routine dampness from the building itself, or from a leak the landlord should have repaired, generally lands on the landlord. If yours is refusing to properly address mold, it may be worth getting guidance about your options.
This is general information about California tenant rights, not legal advice. Every situation is different.