The Progressive Socialist Party was founded on 1949. The founders comprised six individuals, all of different backgrounds, Kamal Junblat, Farid Joubran, Albert Adeeb, Abdallah Alayli, Fouad Rizk, and George Hanna. The party is known to represent the traditional left socialist Marxist line in Lebanon.
The Socialist party may have had non Druze perty members before the war but the party later on consisted of exclusively druze members.
The PSP held in Beirut the first conference for the Socialist Arab Parties in Lebanon, Syria, Egypt and Iraq in 1951. From 1951 through 1972 the party had between three and six deputies in parliament.
The PSP under the leardership of Kamal Jumblat was a major element in the Lebanese National Movement (LNM). Despite Jumblat's initial reluctance to engage in paramilitarism, it built a powerful private army, which proved to be one of the strongest in the Lebanese Civil War of 1975 to 1990. It conquered much of Mount Lebanon and the Chouf District.
At the beginning of the Lebanese war the socialists opposed strongly the Syrian military intervention in Lebanon. They also considered the maronite political power in Lebanon an oppression and the traditional capitalism in Lebanon, they were the leaders of the 1958 revolution against President Kamil Shamoun. The Socialist were also the fiercest defenders of the Palestinian revolutionists in Lebanon and announced an open support to their cause and struggle.
The PSP suffered a major setback in 1977, when Kamal Jumblat was assassinated. His son Walid succeeded him as leader of the party. The Socialist had fierce battles at the beginning of the war against the Phalange, then they clashed with the 'mourabitoun', later they clashed also with Amal movement.
The Socialists allied with the communists lead the two fierce wars against the Lebanese Forces and General Aoun's army.
From the Israeli withdrawal from the Chouf in 1983 to the end of the civil war, the PSP ran a highly effective civil administration, the Civil Administration of the Mountain, in the area under its control. The administration succeeded in providing a high standard of social and public services.
Since the restoration of constitutional rule in 1989, PSP leader Walid Jumblat participated in a number of governments, but, after the Syrian Accountability Act and the UN Resolution 1559, joined the opposition and took up a position opposed to the role of Syria in Lebanon's politics. Unlike some opponents of the Syrian presence, he did not oppose the presence of the Syrian army, but contended that the Syrian intelligence services were exerting undue influence.
Following the passage of United Nations Security Council Resolution 1559, calling for a Syrian withdrawal from Lebanon, Jumblatt was particularly prominent in the opposition. However, he was opposed to the demand that Hezbollah be disarmed, and insisted on maintaining relations with the Shiit Islamist party. Later, he has drifted into sharp opposition towards the group, and has decided to support their disarmament, claiming that Syria and Iran are trying to take over Lebanon through Hezbollah.