Self-esteem relates most strongly to neuroticism, in the negative direction, and next to extraversion; its links to conscientiousness, openness and agreeableness are small. It is not one of the Big Five, but a person’s self-esteem score can be guessed fairly well from their neuroticism and extraversion scores alone.
The evidence
Robins and others (2001) measured self-esteem and the Big Five in a very large internet sample and found the pattern that every later study has repeated. Self-esteem correlated about .5 with emotional stability (the opposite end of neuroticism), about .4 with extraversion, and more weakly with conscientiousness, openness and agreeableness, in that order. The pattern held at every age from early adolescence to old age and in both sexes. People who are calm and sociable tend to value themselves; people who are prone to worry and self-doubt tend not to.
The link with neuroticism is so strong that some researchers treat the two as parts of one thing. Judge and others (2002) found that self-esteem, emotional stability, generalised self-efficacy and locus of control were so closely related that they behaved as indicators of a single broad evaluation of oneself. Orth and Robins (2014) note that self-esteem also follows the same developmental curve as emotional stability, rising through adulthood and falling in old age, which is what you would expect of close relatives.
What the relation does not mean
It does not mean self-esteem is just low neuroticism. A correlation of .5 leaves most of the variation in self-esteem unexplained by neuroticism, and the two scales ask different questions: the neuroticism items ask how often you worry or get upset, the self-esteem items ask whether you are a person of worth. Plenty of people worry a great deal and still like themselves.
It does not mean a low self-esteem score is a verdict on your personality. The Big Five describe tendencies; so does the Rosenberg scale, and a score on either is not a diagnosis of anything. It does not mean introverts have low self-esteem: the link with extraversion is moderate, and the quiet, contented person is common.
What it means for your results
If you have taken both the self-esteem test and a Big Five test, expect them to agree in a loose way: a low neuroticism score usually sits beside a high self-esteem score, and a high extraversion score usually sits beside a higher one. Where they disagree, the self-esteem score is telling you something the Big Five did not. A calm, outgoing person with low self-esteem is unusual, and the score is worth taking seriously as information rather than noise.
The self-esteem test takes two minutes and is scored on your device. If you have a Big Five result saved, the neuroticism page explains the facets that sit closest to it.