Most of the rock hewn and cave churches of Ethiopia to the west and south of Lalibela have escaped the notices of scholars who in different times visited the rock hewn churches of Lalibela and its surroundings. Nazugn Maryam, one of the ancient rock hewn churches of this area is neither scholarly researched nor professionally conserved. The main objective of this study was to document the architecture and the conservation problems of this hypogeum. Data of the study was collected through interview, field observation and analysis of the archives. The study intimates that the church is traditionally believed to have been carved by Abunä Musé, who is regarded as the second bishop of Ethiopia. Being carved out of a single rock, it is rectangular and monolithic. Pointed and arched styles of both opened and false windows, buttresses, and horizontal beam are some of the dominant architectures of the church projected on its exterior facades. Internally it has a basilica with aisles divided by pillars, with no arches and capitals. However, its architectural values are deteriorating due to natural agents such as torrential summer rainfall and sunlight. Besides, the elements attempt at conservation since 1950s have also contributed to its deterioration. New materials like cement and basaltic stone were introduced during the restoration and this has exacerbated its deterioration endangering this important hypogeum. This paper examines how this introduction of new material poses challenges to the future conservation decisions.