Military personnel worldwide Kenya included are engaged in long and protracted operations in faraway places from home. During such deployments, physical separation, poor communication, loneliness, confusion, uncertainty, temptation, rumors, financial problems including risk of injury and death take place thereby affecting the psychosocial well-being of families that are left at home. The purpose of this study was to investigate the effect of Kenya Defense Forces military deployment on the psychosocial wellbeing of their families during the absence of their spouses in Nairobi City County. The study was guided by the specific objectives which sought to: determine the effect of military deployment on psychological wellbeing of the families; establish the effects of military deployment on social wellbeing of their families; explore the effects of the deployment on academic performance of their children; find out the coping mechanisms adopted by the families; and establish possible measures to mitigate against negative effects of deployment on psychosocial wellbeing of the families in Nairobi City County. The study was premised on Family Stability Theory, as the theoretical underpinning. The study adopted a cross sectional survey research design employing both qualitative and quantitative methods. The study targeted a population of 3000 families of military personnel deployed in conflict and peace keeping missions around the world residing in Nairobi City County. The study employed snowballing, stratified random, and convenience sampling to select 61 participants. Questionnaires was the main instrument of data collection for the respondents. The quantitative data was edited, coded, classified on the basis of similarity and then analyzed using Statistical Packages for Social Sciences (SPSS) version 22.0 software, whereas qualitative data was categorized thematically and presented through narration. The findings were presented by way of frequency distributions, percentages, means and standard deviation. The findings established that the psychological wellbeing of the respondents was affected as shown by 82% were overwhelmed by uncertainty feelings upon deployment of their spouses; 80.3% of the respondents experienced social loneliness and sleepless nights; 70.5% had deterioration of academic performance; as 50.8% service personnel resorted to multitasking; and 83.6% proposed counseling as mitigating measures. Overall, the study findings show that there was negative psychological effect with 93.4%. The study concluded that military deployment has a negative effect on the psychological wellbeing of the families left behind leading to prayers, counseling and other measures to mitigate against negative effects of deployment of the military personnel. The study recommended families be provided with regular counseling, financial support, and communication between military personnel. The study suggested that further exploratory study should be done to establish the influence of spirituality on psychological wellbeing of families of deployed soldiers.