Human is a social being and continues as the part of a group in every field of life from the birth. Group isrna community consisting of one or more individuals who interact with each other in order to accomplish arncertain goal. The groups are created formally and informally within the organization at different times andrnfor different goals. Those groups have the negative and positive influences on the organizations’ andrnemployee’s performance. Through informal groups in the organization can develop their own norms andrninfluence that may difficulties the objectives of the formal organizational working conditions. Thernobjective of this study was to assess the influence of informal groups on employee’s and organizationalrnperformance in Amref Health Africa in Ethiopia. Embedded (mixed) survey was the design used for thisrnstudy. Three departments were selected program department, Finance and HR & administrativerndepartments and used random sampling technique. The population was 165 employees. Out of this, 116rnemployees were selected as sample size. The data used for this study included both questioner andrninterview. Questionnaire with both open-ended and close-ended questions was used to collect the primaryrndata. In terms of analyzing the data collected, both quantitative and qualitative methods of analysis werernused. Findings from the study confirm that in connection with the status of informal groups and effect ofrnInformal groups on employee’s performance was very high influence on employees and organizationalrnperformance. Also Informal Groups’ for organizational task achievement have no significant contributionrnon performance. In conclusion therefore the existence of informal groups is risky and influential to hinderrnemployee’s and organizations’ performance of Amref Health Africa in Ethiopia. It is thereforernrecommended that in order to enhance employees and organizations’ performance, heads of managementsrnshould implement proper formal communication channel to make sound decision and to have equal jobrnopportunities within the organization, discourage informal group’s participative discussions on employeesrnand organizations’ task related issue, eliminate conflict between management and employees in related torninformal groups influence and make it transparency an organizational culture and norm