By 2018, many items inside the building had deteriorated, so Notre Dame Cathedral began to be restored and is still ongoing with a cost of 140 billion VND, expected to be completed in 2023 but extended to 2027 due to Covid.

Because during the construction of the cathedral, the French used all the materials from France to build it, the restoration and renovation also used materials imported from France.

In particular, the decorative material on the top of the cathedral roof does not use cement (because the heat will crack). Father Ho Van Xuan, the main project manager, added: "We use a special mortar mixed in a specific ratio, moisturize for 28 days, and then turn it into non-cracking stone."