There is an indulgence now associated with this novena. (The following is from this site.)
On 29 June 2002, the Apostolic Penitentiary of the Holy See promulgated a decree creating new indulgences that may be gained by the faithful in connection with the celebration of Divine Mercy Sunday. This decree grants a plenary indulgence to those who comply with all the conditions established, and a partial indulgence to those who incompletely fulfill the conditions.
Three conditions for the plenary indulgence
And so the Supreme Pontiff, motivated by an ardent desire to foster in Christians this devotion to Divine Mercy as much as possible in the hope of offering great spiritual fruit to the faithful, in the Audience granted on 13 June 2002, to those Responsible for the Apostolic Penitentiary, granted the following Indulgences:
a plenary indulgence, granted under the usual conditions (sacramental confession, Eucharistic communion and prayer for the intentions of Supreme Pontiff) to the faithful who, on the Second Sunday of Easter or Divine Mercy Sunday, in any church or chapel, in a spirit that is completely detached from the affection for a sin, even a venial sin, take part in the prayers and devotions held in honour of Divine Mercy, or who, in the presence of the Blessed Sacrament exposed or reserved in the tabernacle, recite the Our Father and the Creed, adding a devout prayer to the merciful Lord Jesus (e.g. Merciful Jesus, I trust in you!");
A partial indulgence, granted to the faithful who, at least with a contrite heart, pray to the merciful Lord Jesus a legitimately approved invocation.