This research article aims in critically analyzing the strengths and weaknesses of customs and treaties as a source of law in the field of International Humanitarian Law. It deals with the meaning, types brief history, strengths and weaknesses of having customs and treaties as a source of International Humanitarian Law along with some examples as to how International Law has been implemented. Based on the timeline so far, we can observe that certain customs and traditions by itself are not morally correct and must be avoided. In India itself, we have witnessed certain customs such as sati and so on, which later on has been abolished. Hence, there are evidences wherein custom fails to render justice. However, despite this, it is important to know that International Humanitarian Law has played a vital role in not only protecting civilians, but also possibly stopping World War III and using Nuclear weapons through diplomatic communications and treaties. Therefore, there are both pros and cons in taking customs and treaties as sources of International Humanitarian Law and we must appreciate its growth