Pieter van der Werff was a Dutch Golden Age painter. He assisted his older brother, Adriaen van der Werff.
He learned to paint from his brother Adriaen and according to the RKD, he spent most of his life working in Rotterdam, where he painted the rich and famous. There is possible evidence he might have travelled to England to seek commissions as two portraits painted c.1709 attributed to unknown Gentleman and unknown woman, hang in the Victoria Art Gallery Bath. Their alternative titles being John Churchill, First Duke of Marlborough and Sarah, Duchess of Marlborough. Whilst in England he may have had commissions from the Fairfax family -a long established Yorkshire Catholic family who owned extensive land and property in the county.