Anslo was born at Amsterdam and brought up a Mennonite.His family originated from Christiania, now Oslo (Norway).

Early civic fame as a poet came to him in Amsterdam, when he was rewarded by his with a laurel crown and a silver dish for a poem in honour of the foundation stone of the new town hall in 1648.

[2] In December 1651 he was received into the Catholic Church, together with forty-three others, as is shown by manuscript records of the Society of Jesus.

[3] He proceeded to Rome, where he became secretary to Cardinal Luigi Capponi, and received from Pope Innocent X a gold medal for his poetical labours.

They include a tragedy, "The Parisian Blood-Bridal" (De parysche bloed-bruiloff, 1649), dealing with the Massacre of St. Bartholomew.