Inter-clan conflicts are widely spread in the world Africa leading in such cases. Conflict management and peace building in Kenya continues to face challenges in the current national and regional environments. Clans in Mumias East Sub-County have been in conflict from time immemorial. Strategic coordination amongst key actors has been seemingly lacking in conflict management and peace building. The general objective of the study was to examine inter-clan conflicts influence on socio-economic development in Mumias East Sub-County, Kenya. The Objective of this study was to examine the nature and extent of inter-clan conflicts in Mumias East Sub-County, Kenya. Theories employed were; Intergroup Contact theory and linear stages of growth theory. The study employed descriptive, Evaluation, Historical, Ranking and cross sectional research designs. The study population comprised Assistant-Chiefs, Clan Chairpersons, MCAs, Ward Administrators, CBOs, Religious Leaders, deputy County commissioners, Assistant County Commissioners, Sub-County Administrator, Police, Probation Officer, Village Elders, Chiefs and Households Heads totaling to 475 respondents. Primary Data collection was done using Questionnaires, Interviews schedules, Observations checklists, and focus Group Discussion (FGD) guides. Secondary sources included relevant documents and reports. Qualitative data was   analyzed using thematic narratives. Quantitative data was analyzed using Statistical Package for the Social Sciences (SPSS) and Microsoft excel to obtain measures of central tendency, Ranking was done and Charts were used to present data.  Results indicate that majority of the respondents 47% agreed that conflicts occur very often in Mumias East Sub-County. The study sought to establish the extent of inter-clan conflicts in relation to gender, age, occupation, Marital status level of education,  per location and in shopping centres. The types of conflicts addressed are; leadership wrangles, land ownership, land boundaries, political competion and resource distribution. The study established that (48.7%) strongly agree that inter-clan conflicts disrupt learning in Mumias East Sub-County. For the effects on property, (49.9%) strongly agreed that residents of Mumias East lost property during conflicts. Majority of the respondents (78%) agree that a number of development projects in the study area stalled due to inter-clan conflicts.