Dissertation (MA Demography)The influence of in-laws towards married women’s fertility seems to be trivial to many scholars, particularly in Tanzania. This work examined the influence of in- laws towards married women’s fertility in Kaliua District in Tabora Region. It examined the factors affecting married women’s control of their fertility including the influence of in-laws, and extended family on the husband’s decision on the number of children to have and on couple’s decision-making process on how many children to have during the reproductive age. The study used questionnaires, interviews guide, and documentary reviews in collecting data. The findings of the study show that the mothers-in-law, fathers- in-law, sisters-in-law, and brothers-in-law have influence towards the married women’s fertility. These results are consistent with Germany data, which shows that women residing close to parents or in-laws are more likely to have children in close intervals (Mor an, 2012). It is recommended that more research in this area should be done, especially on population policy formulation. If the truth comes in correlation with the findings obtained then it will be more delighting on tackling population issues.