With one round to go before the winter break, Dinamo have 46 points from 18 games, seven more than Rijeka.
The visitors made a brighter start and missed several good chances before midfielder Arijan Ademi gave Dinamo a 40th-minute lead, steering the ball goalkeeper Ivan Vargic after he was put through by Domagoj Antolic.
The home side dominated the second half and were denied a bigger win by a combination of good saves from Vargic and their own slack finishing.
Chile striker Angelo Henriquez, on loan at Dinamo from Manchester United, made it 2-0 shortly after the break, racing clear after another defence-splitting pass from the lively Antolic.
The league’s top scorer Andrej Kramaric missed a gilt-edged chance to pull one back midway through the second half when he scuffed his shot wide from close range.
Rijeka were punished after Junior Fernandes released fellow substitute Duje Cop and the striker side-footed his shot into the bottom left corner.
(Writing by Zoran Milosavljevic in Belgrade, editing by Ed Osmond)
