Gresham was admitted a liveryman of the Worshipful Company of Mercers in 1507. As a mercer, he was in partnership with his brother, John Gresham, in exporting textiles and importing grain from the continent. He supplied King Henry VIII with arras, velvets, and satins. Most of his trade was with the Low Countries, which were the most significant area for English overseas trade for most of the sixteenth century, and he amassed a large fortune. He became Sheriff of London and Middlesex in 1531, and was knighted the same year. On 19 May 1536, he was present at the execution of Anne Boleyn in the Tower of London. He was elected as Lord Mayor of London in 1537, and when Cardinal Wolsey was on his death bed he called Gresham his "fast-friend". Gresham paid for the Cardinal's funeral.