The following is adapted from an article on Wikipedia titled Westminster Larger Catechism.

In 1643 when the Parliament of England called the Westminster Assembly to produce the Westminster Confession of Faith, it also asked for a directory of "catechising". The Assembly tasked Herbert Palmer with producing a draft. However, Robert Baillie and other Scottish delegates found the resulting work disappointing.

Later in December 1643 a committee was formed to write the Catechism. In January 1647 the Assembly split the one catechism into two: the Westminster Shorter Catechism was to be "easier to read and concise for beginners", and the Larger Catechism was to be "more exact and comprehensive".

Both Catechisms were completed by the Westminster Assembly in 1647 and were adopted by the General Assembly of the Church of Scotland in 1648.