Comintern (Communist International, 1919-1943) files kept in a Russian Archive were opened to the public in 1991. Various documents relating to the Malayan Communist Party (MCP) were contained therein. Relying on these documents, this research reveals many important and hitherto unknown facts. Consulting with previous works done by C.F. Yong, Cheah Boon Kheng and others, we can identify the extent to which the British colonial Special Branch intercepted them. The inaugural congress of the MCP, which initially depended heavily on the Comintern’s instructions, was held on 22-23 April and 21 May 1930. Consistent pivotal points of the instructions were to refrain from armed insurgency and to make every effort to obtain the support of Malays and Indians. Although instructions were stopped after 1935, the MCP continued sending reports until the Pacific War started. These reports depict its internal disputes between the left wing and the right wing, which is supposed to have been headed by Lai Teck. Without instructions from the Comintern, the MCP further strengthened its influence among the people through labour as well as anti-Japanese movements.