Tan Po Goan was born in Cianjur, Batavia Residency, Dutch East Indies (now in West Java, Indonesia) on 24 October 1911.

[6][7][2] He worked there for two years, and in January 1939 he requested and obtained an honourary discharge and returned to Java, taking up a similar post at the Raad van Justitie in Surabaya.

[9] He continued working as a lawyer and writing for Sin Po until the Japanese invasion of the Dutch East Indies in 1942; during this era he was a popular and well-connected figure and known as a bon vivant.

[5][7] He was freed after the end of the war and became involved in politics in newly independent Indonesia, and was a supporter of the Republican side against the Dutch in the Indonesian National Revolution.

[7][5] The Indonesian Republic offered the opportunity for people of Chinese descent to become citizens; under the Dutch system, they had been considered subjects of China.

[15][16] He did face some difficulties; in early 1947 he was accused of blocking the evacuation of Chinese Indonesians from Republican to Dutch-held territory; he denied it and insisted that it was the Dutch who had limited the number of refugees they were allowing into the parts of Java they controlled.

[23] He was also briefly a member of the Chinese Indonesian Democratic Party (Partai Demokrat Tionghoa Indonesia, PDTI) for a time, though he formally left it in 1953.

At that time the censorship laws from the Dutch East Indies were still in force in Indonesia, and in late 1953 he advanced a motion to defend the national journalist's union from persecution by Minister of Information Ferdinand Lumban Tobing.

[31] The following summer, he advanced a cross-party motion to finally do away with the Dutch press censorship laws; in this he enlisted the support parliamentarians Peris Pardede and Siauw Giok Tjhan (PKI), Yunan Nasution (Masyumi), Rasuna Said (unaffiliated).

[39][35] Tan's non-confidence measure was eventually defeated in the house in mid-April 1955, but the process revealed some embarrassing documents showing the government had mishandled the situation with Tjong.

[7][49][50] Supposedly part of his reason for withdrawing from BAPERKI was that they wanted to dictate which positions he was to take in the House, and also concerns that it was becoming increasingly close to the Communist Party.

[7] Feeling alienated by the direction of Indonesian politics thereafter, and possibly worried about being arrested in connection with the Permesta rebellion, he stayed abroad for a decade.