Knežević is best-known as portraitist, having produced more than 200 portraits, mostly of notable people of his time.

During his time in Serbia he supported himself by painting portraits of the local nobility and prominent citizens.

This made it difficult for Knežević to earn enough to support himself, let alone to save enough for his education in Vienna.

Even the royal family refused to pay for the many portraits, coats of arms and other symbols that Knežević made for them.

[citation needed] Finally, he found well-paying work in painting walls and icons for Belgrade churches.