Can I work in Germany on a language course visa?

Yes — up to 20 hours a week. This is frequently reported incorrectly online, yet it is stated plainly in the statute.

§ 16f (3) of the Residence Act, word for word:

"Die Aufenthaltserlaubnis nach Absatz 1 zur Teilnahme an einem Sprachkurs berechtigt nur zur Ausübung einer Beschäftigung von bis zu 20 Stunden je Woche."

("A residence permit under subsection 1 for participation in a language course entitles the holder to employment of up to 20 hours per week.") The word nur sets a ceiling; it is not a prohibition.

Note the contrast inside the same provision: permits issued for a pupil exchange or for school attendance (§ 16f (2)) carry no right to work at all. Because all three cases sit in one section, they are often confused.

Two practical points:

1. Your course already runs at a minimum of 18 hours a week. Adding 20 hours of work is demanding, and your permit depends on attending the course.
2. At the visa stage you cannot rely on future earnings to prove your living costs — a blocked account or a formal declaration of support is still required. Work does not replace that proof.

Source: § 16f Residence Act — full text

This is general information, not legal advice.