In this paper, we aim to present an overarching picture of Mathematical Problem Solving (MPP) with a focus on the impact of task variables on MPP products and processes. Admittedly, there are many different settings with which to approach research related to task variables and their associated products and processes in MPP among mathematics students and teachers. In this paper, we approached related research in three kinds of settings: (1) the individual setting, (2) the group setting, and (3) the classroom setting. We then provide some theoretical considerations and literature review in examining task variables in MPP based on four questions: (1) What variables are considered in research on MPP? (2) What methods do researchers use to examine variables in MPP? (3) What do we learn from research on variables about MPP? (4) What might be future directions of research on MPP involving variables?