In the early 20th century. In this era, the castle and its surrounding lands found a new custodian in Joseph Hatch (born 1851), a prominent dairy man from 6 Lower Leeson Street. Serving as a dedicated member of Dublin City Council for Fitzwilliam Ward from 1895 to 1907, Joseph Hatch acquired the castle in the early 1900s to provide ample grazing land for his cattle.

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Passionate about preserving the heritage, Joseph Hatch undertook the restoration of the castle, transforming it into a charming summer retreat for his family. The castle also served as the picturesque venue for significant family milestones, including the celebration of Joseph and his wife Mary Connell's silver wedding anniversary and the marriage of their eldest daughter, Mary, in 1910.

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Following Joseph Hatch's passing in April 1918, the castle became the legacy of his eldest son, Joseph Aloysius, affectionately known as Louis. Alongside his brother Hugh, Louis managed the family dairy farm and the accompanying dairy shop on Lower Leeson Street. Despite never marrying, Louis dedicated himself to the estate until his death in December 1951. Hugh, who married at the age of 60 in 1944, passed away in 1950.

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The Hatch family continued to occupy Drimnagh Castle until the mid-1950s. Subsequently, Louis Hatch bequeathed the estate to Dr.P. Dunne, the Bishop of Nara. Dr Dunne, in turn, sold the castle (allegedly for a nominal sum) to the Christian Brothers. This transaction paved the way for the construction of the school that now proudly stands adjacent to the castle.