PUSPATI TRIGA Reactor (RTP) is the only nuclear research reactor in Malaysia. It has been safely operated and maintained since 28 June 1982. Over 28 years of operation, some of the reactor systems have been upgraded or replaced to ensure the functionality and safety of the reactor. One of the major reactor systems which is primary cooling system is used to remove heat generated in the reactor core. The former primary cooling system consisting of single unit of shell-and-tube heat exchanger, three centrifugal pumps and piping system was replaced with a new system due to decreasing of the cooling performance. The new primary cooling system, consisting of two units of the 1.5-MW plate-type heat exchangers, new three primary pumps and new piping system was installed in accordance to the specified AELB requirements and guidelines of Nuclear Malaysia Safety, Health and Environment Committee (JKSHE). This paper summarises the replacement process of the former RTP primary cooling system. The activities involved preparation before and during construction and installation phases as well as safety consideration based on International Atomic Energy Agency (IAEA), Atomic Energy Licensing Board (AELB) requirements and Occupational Health and Safety Act (Act 514) were discussed and evaluated.