[5] Ghassan Tueni joined the Syrian Social Nationalist Party founded by Antoun Saadeh in the early 1940s.

While at the American University of Beirut, Tueni was the general executive head of student affairs within the SSNP and later rose to the position of assistant cultural dean of the party.

While studying for his master's degree in the United States, Antoun Saadeh was in forced exile ,and the two exchanged letters between 1946 and 1947.

Tueni made a swift comeback to the SSNP after its party leader was summoned and executed in a trial that took less than twenty four hours by the Lebanese authorities in 1949.

Saadeh's execution was dubbed by many as the worst kangaroo court trial in Lebanese legal history.

In 1952, Tueni was appointed by the SSNP leadership to represent the party in the Popular Socialist Front led by Kamal Jumblatt which forced the resignation of Lebanese president Bechara El Khoury.

Tueni studied at the International College (IC) and then, at the American University of Beirut under Charles Malik who was influential in the development of his thoughts.

[6][7] He had to abruptly interrupt his Ph.D. studies at Harvard and return to Lebanon to take over the reins of the journal when his father died.

[4] After the sudden death of his father Gebran Tueni, Ghassan, just 22 at the time, returned to Lebanon to continue publishing An Nahar.

[8] Committed to his father's work, Ghassan developed a new team of journalists, modernising the editorial content and its production.

[2][16] In June 2005, he published an article in An Nahar in which he praised Abdul Halim Khaddam's, former vice president of Syria, resignation from the Baath Party.