Marital infidelity is one of the factors militating against marriage and family which are two institutions that work towards the population and growth of the society. This research study is undertaken to make a little contribution towards creating awareness of the ills of marital infidelity in Idemili North L.G.A.; and to search for the most likely causes and solutions to the problem. The research adopted the systematic sampling approach for the study with a sampling size of 530 respondents. The respondents were drawn from various communities within the Local Government Area, covering the market women and men, civil servants, independent workers and police men and women working within the Local Government Area. The research study was able to make some findings, some of which are, that marital infidelity is very rampant the Area of study; and that it is most rampant among the married couples of age bracket of 25-35 and 36-45. The research made a number of recommendations on the problem of marital infidelity. Some of these recommendations are, that churches and Christian organizations of married men and women should establish marriage counseling centres in the Local Government Area; and that victims of marital infidelity should be encouraged not to resort to divorce and separation.