Johnson was born in London, to German/Flemish migrant parents. His early life is undocumented with the first reference, after his baptism in 1593, to his arrival in London in 1619 from Amsterdam. The quality and style of his work suggests he was at least partly trained in the Netherlands. By the 1620s he had a studio in Blackfriars in London, where he painted high quality portraits of the gentry, merchants and courtiers. His work is characterised by his attention to detail, particularly in the depiction of costume and jewellery. In 1632 Johnson was appointed as ‘his Majesty’s servant in ye quality of Picture drawer’ to Charles I.