He received a solid musical education as a pupil of Heinrich Schütz (d. 1672), and in 1674 joined the Dresden Hofkapelle, where his father, a former Swedish cavalry officer, Friedrich von Westhoff worked.
The Hofkapelle had a strong violin tradition that started with Carlo Farina's publications of the 1620s, and was continued and supported during Westhoff's time by the celebrated violinist Johann Jakob Walther and operatic composer Nicolaus Adam Strungk.
Contemporaries ranked him, along with Heinrich Ignaz Franz Biber and Johann Jakob Walther, among the best German violinists of the era.
His influence must have spread wide, too, since journeys took him to numerous countries: Hungary, Italy, France (where he played before Louis XIV in 1682), the Dutch Republic, and the imperial court in Vienna.
The first was a sonata for violin and basso continuo published in the December 1682 issue—apparently the piece Westhoff played for Louis XIV, which the king greatly admired.
Westhoff's solo violin music is distinctly German, with dense polyphony and robust themes, but the continuo sonatas show a pronounced Italian influence.