This research is about Costa Rica Security. It examines how a country like Costa Rica manage some security challenges induced by its northern neighbour - Nicaragua from 1948 to 1980 when Costa Rica abolished its armed forces in 1948. To ascertain the above mentioned ideas, this research highlighted three objectives that it would be like to accomplish. First, it seeks to identify many different reasons often given to explain Costa Rica decision demilitarising its armed force in 1948. Second, this research evaluates some policy mechanisms available for Costa Rica to maintain its own security. Third, this research examines the policy implementation of the security mechanisms and the impact of demilitarisation to Costa Rica. To help explain the issue, this research utilised a Social Constructivism theoretical framework and a 'structured - systematic causal inference analysis' that helped assessed the plausible number of relationship to explain Costa Rica's security dimension after demilitarisation. As a result, it was found in this research that from 1948-1980 Costa Rica alone could not obtain security primarily by using its own capabilities especially in defending its sovereignty against any form of military aggressions made by Nicaragua. Thus, the defence system of the country depends (to a certain extent rely fundamentally) on the aid of other states or institutions (through the help of the US and security community such as Organisation of American States (OAS). It is also found that the second mechanism was only applied by Costa Rica when the country received immediate and obvious military threat from Nicaragua. Astoundingly, Costa Rica had also pragmatically take advantage from the insurrection movement made by Frente Sandinista de Liberacion Nacional (FSLN) as its third mechanism to secure its position vis--̉vis its northern neighbour. Indeed, element of unarmed diplomacy based on Costa Rican culture and identity has been fully utilised to support the above mentioned security mechanisms in which it also acts as the frontier of its defensive security system.