Simon Marks was playing for Dora Creek Workers Cricket Club at Pickering Oval in Adamstown Heights. The other man, who has not been identified, was playing for Bonnells Bay-based Newcastle Bay Hotel Cricket Club at Waterboard Oval in Blackalls Park.
Both players collapsed when batting.
They were unable to be revived despite the best efforts of teammates and opponents who performed CPR before ambulances arrived.
Newcastle and City Suburban Cricket Association (NCSCA) confirmed the incidents via a statement on Sunday.
"It is with sadness that we inform all members of our association, that two playing members passed away while playing cricket," Wes Inglis posted online on behalf of NCSCA.
"The association, players and umpires wish to pass on our sincere condolences to the families and teammates of these two gentlemen and to all players involved in both matches.
"We praise all involved for doing their best in this difficult situation, by performing CPR on both players til the ambulances arrived.
"Players from both opposing teams showed care and true sportsmanship during these tragedies."
Mr Marks, 45, has been remembered as someone who "loved his cricket" by Dora Creek secretary Graham Field.
"Everybody is just shattered," Mr Field said.
Mr Marks played over 160 games for the club since first signing up in 2008-09, scoring 1598 runs and taking 21 wickets. He also had 153 dismissals as a keeper.
Dora Creek were playing a D2-grade fixture against Central Leagues Club on the weekend.
Newcastle Bay Hotel had been up against the Toronto RSL Mudcrabs in a C4-grade encounter.
"Both of these guys where true gentleman of the game and will be sadly missed," Rob Coulthart posted on social media.