The parliamentarian army at Modbury included the force mustered at Kingsbridge consisting of 8,000 militia men and volunteers who were probably mainly infantry.  If many of the volunteers were ‘clubmen’ as claimed by some accounts, they are likely to have had only limited training and improvised weapons, unless the earl of Stamford had managed to equip them when he sent unidentified ‘provisions’ to those mustering. The Plymouth force consisted of Sir John Merrick’s grey coated regiment of foot, probably numbering 800-900 men at this time, 400 cavalry and dragoons as well as some volunteers. In all about 1,500 men.  The Kingsbridge and/or Plymouth force also had an unknown quantity of artillery with them as the accounts of the battle are clear the parliamentarians bombarded the royalist defences in Modbury.

The royalist army at Modbury consisted of two foot regiments under Sir Nicholas Slanning and Sir John Trevanion with five pieces of ordnance, along with some cavalry and dragoons; around 1,500 men in total.