Prayed on ordinary Rosary beads, The Chaplet of Divine Mercy is an intercessory prayer that extends the offering of the Eucharist, so it is especially appropriate to recite it after having received Holy Communion at Holy Mass.
It is likewise appropriate to pray the Chaplet during the “Hour of Great Mercy” – three o’clock each afternoon (recalling the time of Christ’s death on the cross). In His revelations to St. Faustina, Our Lord asked for a special remembrance of His Passion at that hour.