In Amsterdam, van Loo found himself at the centre of an active and competitive circle of artists, which included Rembrandt, Frans Hals and Bartholomeus van der Helst. Around 1640 Eglon van der Neer entered his studio as an apprentice and remained his student for a decade. In 1652 van Loo bought himself citizenship ("burgerrecht") of the city of Amsterdam. It was speculated that he did so in the hope of being commissioned to help decorate the newly constructed town hall. In 1654, a poem by Jan Vos counted van Loo among the most significant of Dutch painters, alongside Rembrandt and van der Helst.