Universalization of Primary Education and eradication of Child Labour are world’s common issues. There is a dire need to explore and search out the root causes of these two opponent issues those which reciprocate each other. This study tries to unveil all the visible and invisible forces behind these issues which not only hinder Universalization of Primary Education, but also escalate Child Labour. The main reasons for Child Labour in many countries including Pakistan and particularly in the 3rd world nations is lack of basic education which is mainly caused by poverty, lack of educational institutions, community participation, enrollment campaigns, location, socio-economic of the child’s family, family background, gender discrimination, high educational expenses and the dropouts due to teacher’s harsh behaviour. This study attempts to assess and search out the causes of Child Labour and its adverse impact on Universalization of Primary Education at District Bannu. Objectives of this study were: to explore the determinants of Child Labour and Universalization of Primary Education, to identify different factors responsible for Child Labour as perceived by parents of the Child Labourers, to find out different kinds of hurdles in the Universalization of Primary Education as experienced by Teachers and to analyze the impact of Child Labour on Universalization of Primary Education at District Bannu in Khyber Pakhtunkhwa. The study was a blend of different methods for which exploratory sequential design (QUAL+QUAN) was applied by the researcher. The population of current study comprised all the parents or guardians of the total 992 Child Labourers and 2939 teachers teaching at primary level at District Bannu. The sample of the study for Qualitative phase comprised twenty participants for interview (10 male + 10 female Child Labourers). Similarly for Quantitative phase it consisted of 147 teachers and 100 parents/guardians of Child Labourers. For Qualitative data collection 20 open-ended interviews were conducted and for Quantitative data collection a self-developed questionnaire for teachers and a separate structured questionnaire for parents/guardians based on Qualitative findings were distributed among them to know their perceptions regarding Child Labour and Universalization of Primary Education. For Qualitative data analysis NVIVO (V-10) was used which provided determinants in the form of main themes. Similarly for Quantitative data analysis SPSS (V-24) supported by descriptive statistics in terms of percentage, frequency, mean and standard deviation, while ANOVA, Correlation, Regression, Chi square and T-test was used as inferential statistics by the researcher. From the findings it was concluded that Child Labour which is mostly caused by poverty, teacher’s behaviour, child status, family status and location was a real and the biggest challenge for the Universalization of Primary Education. Therefore, it is recommended to the agencies and concerned high ups to eliminate Child Labour through effective implementation of universal compulsory primary education without any further delay.