The study focused on customary laws and the right of windows of Nyamwezi tribe inheriting land in Tanzania. The objectives were: to evaluate the effectiveness customary laws governing land inheritance by Nyamwezi widows and to analyze challenges faced by Nyamwezi widows on application of customary law on land inheritance. The study used the Doctrinal Legal research design. The population was 172 and sample size of 120 calculated using Yamane (1967) formula was used. The sample size was selected using random sampling from the population. The study used both primary and secondary data. The data was collected using questionnaire and documentary methods. The data was analyzed qualitatively and results displayed on tables for easy reporting. The study concluded that, customary laws were not effective on safeguarding widows land inheritance rights and were challenges facing Nyamwezi widows on application of customary law on land inheritance with the highest challenges being, Land titles solely held by men and Corruption in inheritance disputes due arbitrated by local leaders. The study recommended that conflict between customary laws and state legislation should be dealt with by legislating on a unifying widows land inheritance law, establish law enforcement mechanisms which are not biased and cannot be easily corrupted by the local leaders, Ensure women can hold title deeds and advocate for registrations of all customary marriages.