A number of methods like Linear programming, Dynamic programming, Assignment problem, Transportation problem, Game theory etc., are examples of decision making under certainty. When there are uncertainties or vagueness in the data regarding alternatives and criteria, we can use different techniques for decision making based on whether the data involves probabilities, fuzzy sets, soft sets, rough sets and so on. This situation is called Multi-Criteria Decision Making (MCDM) under uncertainty. MCDM is considered to be a sub discipline of operations research that deals with structuring, planning and solving decision problems that involve multiple criteria, with a purpose of supporting decision makers facing such problems. When the numbers of criteria are more than one and conflicting in nature, the solution can no more be unique, it can only be best among the available alternative solutions. This book is the outcome of the research work carried out by us towards finding applicationsof complex cubic set, complex cubic intuitionistic fuzzy set, complex cubic interval valued intuitionistic fuzzy set, complex interval valued Pythagorean fuzzy set and complex cubic Pythagorean fuzzy set.