Moreelse was born and lived most of his life in Utrecht. He was a pupil of the Delft portrait painter Michiel Jansz. van Mierevelt, who had himself been a pupil of Anthonie van Blocklandt. He took a study-trip to Italy, where he received many portrait commissions. Back in Utrecht, in 1596 he became a member of the zadelaarsgilde (Saddler's guild), which then embraced the painters as well. In 1611, along with Abraham Bloemaert, he was one of the founders of a new painters' guild, called "St. Lucas-gilde", and became its first deken.
