What stands today are the weathered ruins of what was once a small tower house, its barrel vaulted ground floor now mostly collapsed and filled with rubble. The north wall, stretching 13.4 metres and rising to 5 metres high, remains the best preserved section alongside the northeast corner; whilst the east wall shows evidence of a blocked doorway amidst its partial collapse. The south and west walls have fared worse, reduced to low wall footings that barely hint at the structure's original form.

Historical records paint an intriguing picture of the site's evolution. The 1913 Ordnance Survey map marks it as 'Boardstown Castle (in Ruins)', showing its subrectangular shape, though curiously no castle appears on the earlier 1654;57 Down Survey map of Mullingar parish. By 1732, the property had become the residence of John L'Estrange, suggesting the castle may have still been habitable or at least incorporated into a functioning estate at that time.

Archaeological surveys from the 1970s and 80s reveal additional layers to Boardstown's history. Grass covered wall footings and rubble extending south from the main ruin are believed to be the remains of a Georgian house that was built directly onto the castle's south side, showing how later generations adapted and expanded the medieval structure for their own purposes. Today, fragments of the castle's past have found new life; window pieces and reused quoin stones have been incorporated into an outhouse in the neighbouring farmyard, ensuring that even in decay, Boardstown Castle continues to be woven into the fabric of the local landscape.