This article takes Karl Gützlaff's diary, which he wrote (in Dutch during his time in the Dutch East Indies), as the main reference to discuss his reasons for leaving the Netherlands Missionary Society and the Dutch East Indies, and becoming a missionary in China. His decision to go to China cannot be attributed to a long-standing interest in China. Rather, it has to be traced back to his contradictions with the Netherlands Missionary Society, and the fact that Gützlaff was eager to become successful and famous. Also, overseas Chinese in Southeast Asia, who were mostly well-educated and wealthy, made a good impression on him. During his time in Southeast Asia, Gützlaff was highly influenced by members of the London Missionary Society, such as Claudius Henry Thomsen and Jacob Tomlin. Some of the early Protestant missionaries had a low social status and thus a low level of education, and acted recklessly. While conducting missionary efforts in China, their work conditions were rather chaotic. Scandals, such as the embezzlement of missionary societies' property, adultery, and reselling opium, occurred frequently. Gützlaff was also later denounced for many immoral deeds, most of which can be traced back to the influence of these missionaries. This is a key aspect to our understanding of Gützlaff, and other early missionaries in China. Moreover, the written accounts of Jahangir Khoja's upheaval in Gützlaff's diary, reveals that due to long-term obstructions to enter China, Protestant missionaries hoped for domestic disorder in China so that the blockade of the coastal areas would be lifted. In the end, being unable to enter China, Gützlaff and Jacob Tomlin decided to travel to Siam as the starting point for their missionary efforts and became the first two Protestant missionaries to arrive there.