The Leinster pair were beaten in the round of 32 and 64 respectively.
Monkstown’s Mari lost to Hungary’s Aitila Bernath in the 51kg class while Italy’s Gianluligi Malanga defeated St Michael Athy’s McCarthy in the 65kg division.
Mari was on the wrong end of a split decision against Bernath and McCarthy dropped a unanimous decision to Malanga.
Today’s events mean Ireland are still looking to register a victory in the latest World Championships installment after Eugene McKeever lost on the opening day.
JP Hale is the next Irish boxer in action and will fight tomorrow (Wednesday).
AIBA World Elite Championships Belgrade Serbia
October 25th (Last 64)
67kh Eugene McKeever (Ireland) lost to Asadhuja Muydinkhajaev (Uzbekistan) 0-5
October 26th (Last 32)
51kg Sean Mari (Ireland) lost to Aitila Bernath (Hungary) 1-4
63kg Brandon McCarthy (Ireland) lost to Gianluligi Malanga (Italy) 0-5
October 27th (Last 64)
JP Hale (Ireland) v Semiz Alicic (Serbia)
October 28th (Last 32)
57kg Adam Hession (Ireland) v Eduard Savvin (RBF)
October 30th Last 32)
Rickey Nesbitt (Ireland) v Nodrjon Mirakhmador (UzbekistaN0
Keylan Cassidy (Ireland v Arriaga OLvera (Mexico)
48 kg. Ricky Nesbitt (Holy Family)
51 kg. Sean Mari (Monkstown)
57 kg. Adam Hession (Monieva)
60 kg. JP Hale (Star)
63kg. Brandon McCarthy (St Michaels Athy)
67 kg. Eugene McKeever (Holy Family)
80 Kg. Kelyan Cassidy (St Saviors/ Crystal)
IABA President, Dom O’Rourke
Team manager, Peter O’Donnell
Coaches, Zaur Antia, Dmitry Dimitruk, Eoin Pluck