The purpose of this study was to describe and analyze a case study of a multicultural family counseling focused on a mother-in-law. This study would provide a case study to prevent multicultural family problems effectively and to develop efficient a counseling program. The research design for this case study was a non-experimental study. I did in-depth interview and observation of an individual, check her with psychological tools, and intervened to mitigate her problem. The subject of this study was one 61 year old elderly woman. She has no problem with her cognition, affection, and communication. She was living with her 30-year-old daughter-in-law who came from Vietnam to live with her Korean husband in Korea. The elderly woman was the mother-in-law in a multicultural family. The result of the study found that the counseling for multicultural family should include parent-in-law, especially mother-in-law. A detailed physical, emotional health assessment, and providing health information of the mother-in-law were also important factor for her in having a good relationship with her daughter-in-law. Major problems of the multicultural family came from the conflicts between mother-in-law and daughter-in-law. In order to intervene into the multicultural familial conflicts, it is very important to investigate the relationship between mother-in-law and daughter-in-law. This paper also shows how to intervene in the conflicts between mother-in-law and daughter-in-law.