He received his episcopal consecration on 25 January 1948 from Patriarch Markos II Khouzam, with Bishops Alexandros Scandar and Pierre Dib serving as co-consecrators.
This was done pursuant to Pope Paul VI's motu propio Ad Purpuratorum Patrum issued only eleven days earlier on 11 February 1965 which decreed that Eastern Patriarchs who are elevated to the College of Cardinals would belong to the order of cardinal-bishops, ranked after the suburbicarian cardinal-bishops, but would not be part of the Roman clergy and would not be assigned any Roman suburbicarian diocese, church or deaconry, their patriarchal see instead becoming their cardinalatial see.
[1] At the Synod of Bishops in 1971, the patriarch expressed his opinion that the Latin Church would be unwise to ordain non-celibate men, believing married priests may become too absorbed with family matters.
At the conclusion of both conclaves, Patriarch Sidarouss was one of the few cardinals in the central balcony of St. Peter's Basilica accompanying the new popes when they first made their appearances to the public on August and October respectively.
He lost the right to participate in any future conclaves upon reaching the age of eighty on 22 February 1984, and resigned the patriarchate on 24 May 1986, after twenty-eight years of service.