The structure likely dates from the 15th or early 16th century, when tower houses were the preferred defensive residences of the Anglo-Norman and Gaelic Irish nobility. These fortified homes were designed to withstand raids whilst providing comfortable accommodation for the lord's family, and Dysart Castle follows this typical pattern with its thick limestone walls and narrow window openings.

The castle's strategic position would have given its inhabitants control over the surrounding fertile farmland and nearby routes through the countryside. Like many Irish tower houses, it would have originally stood four or five storeys tall, with the ground floor used for storage and the upper levels containing the main living quarters. The castle's defensive features include murder holes above the entrance, from which defenders could drop stones or hot liquids on attackers, and bartizans; small turrets projecting from the corners that allowed guards to survey the approaches.

Today, whilst partially ruined, Dysart Castle remains an evocative reminder of Ireland's turbulent medieval past. The ivy-covered walls and empty window frames create an atmospheric site that speaks to centuries of changing fortunes. Though privately owned and not open to the public, the castle can be viewed from the nearby road, where it continues to dominate the local landscape much as it would have done when first built over 500 years ago.