Maslow's primary contribution to psychology is his Hierarchy of Needs. Maslow contended that humans have a number of needs that are instinctoid, that is, innate. These needs are classified as "conative needs," "cognitive needs," and "aesthetic needs." "Neurotic needs" are included in Maslow's theory but do not exist within the hierarchy.

Maslow postulated that needs are arranged in a hierarchy in terms of their potency. Although all needs are instinctive, some are more powerful than others. The lower the need is in the pyramid, the more powerful it is. The higher the need is in the pyramid, the weaker and more distinctly human it is. The lower, or basic, needs on the pyramid are similar to those possessed by non-human animals, but only humans possess the higher needs.

The first four layers of the pyramid are what Maslow called "deficiency needs" or "D-needs:" the individual does not feel anything if they are met, but feels anxious if they are not met. Needs beyond the D-needs are "growth needs," "being values," or "B-needs." When fulfilled, they do not go away; rather, they motivate further.

The base of the pyramid is formed by the physiological needs, including the biological requirements for food, water, air, and sleep.

Once the physiological needs are met, an individual can concentrate on the second level, the need for safety and security. Included here are the needs for structure, order, security, and predictability.

The third level is the need for love and belonging. Included here are the needs for friends and companions, a supportive family, identification with a group, and an intimate relationship.

The fourth level is the esteem needs. This group of needs requires both recognition from other people that results in feelings of prestige, acceptance, and status, and self-esteem that results in feelings of adequacy, competence, and confidence. Lack of satisfaction of the esteem needs results in discouragement and feelings of inferiority.

Finally, self-actualization sits at the apex of the original pyramid.

In 1970 Maslow published a revision to his original 1954 pyramid, adding the cognitive needs (first the need to acquire knowledge, then the need to understand that knowledge) above the need for self-actualization, and the aesthetic needs (the needs to create and/or experience beauty, balance, structure, etc.) at the top of the pyramid. However, not all versions of Maslow's pyramid include the top two levels.

Maslow theorized that unfulfilled cognitive needs can become redirected into neurotic needs. For example, children whose safety needs are not adequately met may grow into adults who compulsively hoard money or possessions . Unlike other needs, however, neurotic needs do not promote health or growth if they are satisfied.

Maslow also proposed that people who have reached self-actualization will sometimes experience a state he referred to as "transcendence," in which they become aware of not only their own fullest potential, but the fullest potential of human beings at large. He described this transcendence and its characteristics in an essay in the posthumously published The Farther Reaches of Human Nature.

Maslow's theory of human needs draws strongly on the pioneering work of Henry Murray (1938). This provides the basis for wide-ranging and extensively validated work relating to achievement, affiliation, power and ambition."We move toward self actualization". This quote brings in Maslow's theory of motivation, tying along with the growth, happiness and satisfaction of every person. He believes to be motivated that it is not driven by reducing tension or avoiding frustration that people look for a positive view.