Sfeir was born in Rayfoun, Lebanon, on 15 May 1920. He was educated in Beirut, and at Mar Abda School in Harharaya where he completed his primary and complementary studies, and Ghazir where he completed his secondary studies at St. Maron seminary. He graduated in philosophy and theology in 1950 at Saint Joseph's University in Beirut. He was ordained to the priesthood in the same year on 7 May. From 1951 to 1955 he served as priest to the parish of Rayfoun. In 1956, he was appointed the secretary of the Maronite Patriarchate, based in Bkerké. In the same year, he became the professor of translation in literature and philosophy at the Frères Maristes (Marist Brothers) School in Jounieh. On 23 June 1961 Sfeir was appointed Titular bishop and Patriarchal vicar. On 16 July 1961, he was consecrated the titular bishop of Tarsus by Patriarch Paul Peter Meouchi and had as his co-consecrators João Chedid, Titular bishop of Arca in Phoenicia dei Maroniti and Michael Doumith, Eparch of Sarba. Consequently, Sfeir served as Patriarchal vicar.
He was elected to the primacy of the Maronite Church by the Council of Maronite Bishops, on 19 April 1986, and he was confirmed by Pope John Paul II on 7 May 1986.
Sfeir is keen on accelerating liturgical reforms. This work bore fruit in 1992 with the publication of a new Maronite Missal, which represents an attempt to return to the original form of the Antiochene Liturgy. Its Service of the Word has been described as far more enriched than previous Missals, and it features six Anaphoras (Eucharistic Prayers).
Serving as the Vicar for two previous patriarchs prepared Sfeir for the role in both the ecclesiastical and civil spheres. He became a strong voice for reason and sanity in the latter years of the Lebanese Civil War, which raged from 1975 to 1990. He has often spoken out against social and political injustices, and for the poor and disenfranchised. His writings and sermons set out his vision of how Lebanon can achieve a free and prosperous future. Like his predecessor, Sfeir largely stayed out of politics during the first few years of his tenure as patriarch, generally deferring to the stance of the Lebanese President, but by 1989, he had become embroiled in national politics.
Cardinal Sfeir submitted his resignation to the Congregation for the Oriental Churches in Rome in late 2010, but his resignation was not initially accepted because six Maronite bishops have submitted their resignations after reaching the retirement age of 75 in June 2010 His resignation was finally accepted by Pope Benedict XVI on 26 February 2011.
Cardinal Sfeir was succeeded by Bishop Bechara Boutros Rahi who was elected as the new Patriarch for Antioch on 15 March 2011.
Sfeir was made a cardinal by Pope John Paul II in the consistory of 26 November 1994. As the Patriarch of a sui juris particular Church who has been made a cardinal, Sfeir is a Cardinal Bishop.
He did not participate in the conclaves of 2005 and 2013, having already reached age 85 and 90 by then.
Sfeir has written several books, including "The sources of the Gospel-Bkerké", (1975); "Personalities that disappeared 1961-1974" - (two volumes); and "Sunday sermons: spiritual reflections and stand of national positions", (several volumes, 1988).
Sfeir is fluent in many languages: Syriac, Aramaic, French, Italian, and Latin, as well as his native Arabic, being proficient in both classical and Lebanese dialects.
The cardinal found himself both within the Syrian camp and outside it. At the beginning of the 1990s he did not support Syria's role against General Michel Aoun. In the spring of 1989, when Aoun launched a campaign to achieve control of militia-dominated areas, 23 Christian deputies of parliament met at the seat of the Maronite Church in Bkerké, under the auspices of Sfeir, and called for a cease-fire. While hundreds of thousands Lebanese (Christians and non-Christians) gathered in the Baadba presidential palace in support for Aoun, a couple of thousands of Christians demonstrated in Bkerki against Aoun. Under what some say was pressure from the Vatican, he backed the Taif Agreement and hence the Syrian mandate over Lebanon in order to end the civil war, saying that it was "a fatal error to believe that we can live alone on an island in which we run our affairs as we like." A few days later, he declared that Aoun's nonacceptance of the Taif Agreement was illegal and unconstitutional. On 5 November, as parliamentary deputies met at an abandoned air base in Syrian-controlled North Lebanon to elect a new president, Sfeir warned in a sermon that Aoun's stand "would lead to partitioning of the country."
The patriarch's authority was challenged even within the Church itself, as several monastic orders issued proclamations supporting Aoun and denouncing the Taif Accord. To bolster the patriarch's authority, the Vatican became directly involved in reorganizing the Maronite Church. Speaking before a gathering of Lebanese bishops in November 1989, the papal nuncio in Lebanon, Pablo Puente, condemned "the interference of clerical persons and institutions in politics without being officially mandated to by the church hierarchy... an end must be put to political visits and declarations that have no clear Church mandate." The Vatican later sought to temper nationalist views in the clergy by appointing "visiting bishops" to supervise three especially militant monastic orders. In 1990 Sfeir called for the rival government in West Beirut to take over Aoun's "Christian enclave" in the east. "The legitimate government should spread its authority over the whole nation," he said in one interview. "It should not wait for an invitation from anyone to do so." Finally on October 13, 1990, the Syrian army crushed Aoun's insurgency and the long civil war finally came to an end. Aoun's main objection to the Taif Accord was that it had no firm timetable for Syrian withdrawal and that it abolished most of the Maronite president's power giving them to the Sunni prime Minister. The Syrians were to occupy Lebanon for another 15 years.
The Syrian invasion was 'forced' under international pressure to withdraw its forces from Lebanon, following the political upheaval and large scale street protests which followed the assassination of former Prime Minister Rafik Hariri (see Cedar revolution); at the end of April 2005 - Sfeir was at times a vocal critic of Syrian prevarication in carrying out its pledge to withdraw, up until around 2003, falling silent again just as anti-Syrian views were becoming more widespread. His restraint in his comments at this time appeared to have lost him the support, in particular, of a majority among those Christians who had fled the country. The Cardinal also urged restraint in anti-Syrian rhetoric, and for Lebanon to focus on its economic development rather than political rifts. Nevertheless, hundreds of thousands of Lebanese (mostly Christians) gathered in Bkerke and the roads leading to it on March 27, 2001, to welcome back the Cardinal from a tour in the United States, during which he asked for the withdrawal of the Syrian army. He blessed in 2001 the establishment of Christian Qornet Shehwan Gathering opposed to the Syrian role and in the aftermath of the Hariri assassination he restated his opposition to Syria's predominant role in Lebanese politics and the political changes following Syrian withdrawal appear to have largely restored his previous position as the main spokesperson for his community.
In the first half of 2006 the Cardinal was critical of the political paralysis created by the controversy over whether President Émile Lahoud should serve the remainder of his term of office (which was specially extended under Syrian pressure in 2004 until November 2007). At the same time, he stressed that Lahoud should be removed only by lawful and constitutional means and that the continued smooth functioning of government and a national consensus on his successor were the main priorities. In order to discuss the July 2006 Israel-Lebanon war and American policy on the affair, he met with Vice President Dick Cheney at the White House, and later talked with Secretary of State Condoleezza Rice.
On 15 October 2006, the Christian Free Patriotic Movement held gatherings in which anti-patriarchal slogans were raised, denouncing Cardinal Sfeir's political stands, which they consider contradictory to the will of the FPM Christians in Lebanon. The FPM bloc, led by retired general and current president Michel Aoun, constitutes the largest Christian bloc in the Lebanese parliament. Relations between The cardinal and The FPM and Hizbullah further deteriorated when the patriarch made an eleventh hour appeal directly before the 2009 elections renouncing Hizbullah and the FPM and warning Christians against voting for them. A stance which many believe to have severely cut Christian support to March 8 Alliance, especially when Aoun emerged as the biggest loser in the 2009 elections according to some estimates. The FPM blame the cardinal for making them lose 20% of Christian support using religious rhetoric, and for not objecting against the transfer of 15,000 sunni voters from Bekaa villages to the Christian district of Zahle which lost the FPM 8 MP's there. Currently the FPM and its allies have one out of twelve orthodox seats, two out of eight catholic seats, two out of six Armenian seats and almost half of maronite seats with the rest belonging to 14 March yet FPM still retains the biggest Christian single parliamentary block of 27 MPs, which includes MPs from other parties such as the Marada Movement as well as independent pro-Syrian government personalities. Also not all of the Change and Reform bloc MPs are Christians.