This study assesses the relationship between maternal attachment on social and emotional adjustment of primary School pupils in South West Nigeria. Eight (8) research objectives, eight (8) research questions and eight (8) null hypotheses guided the study. Descriptive survey design was used for the study. The population consisted of twenty six thousand two hundred and fifty six (26,256) primary school pupils within the age range of 7 - 10 years from 32 schools of the three sampled state in South West Zone Nigeria. Sample size consisted of 647 respondents that were selected through Multistage sampling techniques. Two modified questionnaires modified on a four (4) point rating scale were used as instrument to collect data from respondents. The first questionnaire is titled "Attachment Q-Sort Questionnaire and the second is titled "Child Attachment Scale questionnaire." The questionnaires were validated by experts. Test-retest method of reliability was used to obtain the internal consistencies of the instruments. The reliability index was obtained through reliability statistical method and reliability coefficient of 0.754 was obtained. Data collected were statistically analyzed using the frequency tables, mean score and Pearson Product Moment Correlation Coefficient (PPMCC). 2.50 were taken as the bench mark for decision making. The eight (8) hypotheses raised for the study were tested at p- value of 0.05 level of significance. The tested null hypotheses 1 & 2 revealed that secure maternal attachment had significant relationship on social and emotional adjustment of primary school pupils while hypotheses 3 - 8 revealed that insecure attachment has significant inverse relationship on both social and emotional adjustment of primary school pupils within the age range of 7 - 10 years. The study discovered that the development of insecure maternal attachment among many other factors is the lack of prompt provision of child‟s needs with highest mean response of 3.77 and 3.77 respectively for development of insecure attachment. Also, it was further discovered that, mother‟s failure in maintaining physical contact with the child, weaken the social and emotional adjustments of the pupils. The study concluded that the child has an innate need to attach to one main attachment figure which is more important than any other (usually the mother); a breakdown of which could lead to serious negative consequences. Some of these are lacking in the ability to adjust socially and emotionally in the society. The researcher therefore recommended that, Mothers and caregivers should respond to all needs (physical and emotional) of children in their care so as to establish good reciprocal relationship that will lead the child to develop secure attachment. Workshops and seminars should be organized by Home Economists for mothers on the risk of unstable care giving which promotes insecure avoidant attachment style that leads to social and emotional maladjustment