This research work aims at a study about “Merit” in Theravada Buddhist Philosophy and in Roman Catholic Christian Philosophy, based on data coming from Buddhist scriptures (Tripitaka and) Christian scriptures (the Bible) on this subject. The conclusion of this research work may be summarized as follows : The meaning of the word (merit) is different in Buddhism and in Christian doctrine because, basically, the Buddhist religion is a religion without God (atheism), while Christian religion believes in God. Therefore the essential characteristic of Christian religion is the relationship of love and faith between man and God, while the main characteristic of Buddhism is a faith in the illumination of the Buddha : the 4 noble Truths and a rational understanding or wise consideration (yonisomanasikara). But the similarities between Buddhism and Roman Catholic religion are more to be found at the level of meritorious actions. These actions or deeds which produce merit in Buddhism are alms giving, faithfulness to the Buddhist precepts and meditation. In Christian religion, we find also alms giving, faithfulness to God’s commandments and prayer (expression of faith and faithful relationship to God) or meditation. There the differences are only in the way of acting and in the modes of liturgical or devotional practices. In Buddhism, in order to gain merits, one must work and act by oneself, while in Christian religion, besides personal act or work, one must receive the help and grace from God. Regarding the benefits of merits, we find again some similarities. In Buddhist religion, the purpose of making merits is to get happiness in this present life, especially spiritual happiness or happiness of mind, and happiness in the world to come (Heaven) ; and it is a way to help reach to the final, highest goal : Nirvana. In Christian religion, there is the same purpose of getting happiness, spiritual happiness in this present life, and also the purpose of getting eternal life in the Kingdom of God. If we consider, on both sides, the religious practices which express the belief and meaning of merits, we find two aspects : on the one hand, there are individual practices based on one’s own faith and piety such as giving alms, following the Buddhist precepts or the commandments of God, prayers and meditation, and on the other hand there are common or group practices such as following together the 8 precepts in community, offerings to monks or Kathin offerings for the Buddhists, and devotions to the Blessed Sacrament or other common devotions (for example, the way of the Cross), or again going out to help the poor, for the Catholics. Those who perform such actions believe that their actions produce merits and happiness of mind. Both Buddhism and Christianity have the same belief that liturgical or devotional actions are important, fundamental ways to lead people to a good life and to go up more and more towards perfection.