There is no single Orthodox answer, and that is the honest headline. A convert from Catholicism may be received three ways, depending on jurisdiction and rigor: by profession of faith, by chrismation (the most common practice today, by economy), or by full re-baptism (the strict practice on Mount Athos, among Old Calendarists, and historically in parts of the Russian world). Behind the three methods stands one question, and everything turns on it: is the convert’s Catholic baptism real?

The economia school — the historic and current Ecumenical-Patriarchate mainstream, codified at the Synods of 1484 and Moscow 1667 — chrismates Catholics precisely because it holds their baptism was a true baptism that needs only completing, not repeating; the Moscow synod ruled that “the Latins… do observe a true baptism.” This is the dominant modern practice, and it is worth marking what it concedes: a real sacrament outside the visible boundaries of Orthodoxy.

The akribia (strict) school holds the opposite, and holds it on principle: there are no real sacraments outside the canonical Church, so the convert’s “baptism” is not a defective sacrament but a non-sacrament. St Nicodemus the Hagiorite, in the Pedalion, could call Latin baptism “not a baptism at all but… simply a washing,” and the 1755 Horos of Constantinople under Patriarch Cyril V received Latins “as being unbaptized… and without danger we baptize them.” The rigorist is not a bigot: he revives a real patristic line (Cyprian; Carthage, 256) and presses a concrete complaint — the West’s abandonment of triple immersion — framing his own practice as akribia, the strict truth, with chrismation a permitted economy over a rite he holds void.

The Catholic side is not symmetrical, and that is the point. Rome fully recognizes Orthodox sacraments — baptism, chrismation, orders, Eucharist (Vatican II, Unitatis Redintegratio 15) — and receives an Orthodox convert by profession of faith alone: no re-baptism, no re-chrismation, no re-ordination; an Orthodox priest who becomes Catholic remains a priest. Baptism validly given is never repeated (CCC 1271). So the asymmetry is structural: Rome reciprocates a recognition that the strict East withholds, and to re-baptize the already-baptized is implicitly to deny that his baptism was ever real. Yet notice how narrow the live dispute is — the economia-minded Orthodox and the Catholic Church agree on the decisive premise, that Catholics are truly baptized, and only the rigorists deny it. Economia rightly used presupposes a real baptism to complete; it cannot, by itself, settle whether the grace was there to begin with. On that question much of Orthodoxy already stands with Rome; the asymmetry that remains is for the dialogue to resolve.