France captain Julien Benneteau predicted Halep might be the decisive factor in the meeting between the No.4 and No.5 teams in the Fed Cup rankings, and that proved to be the case in the opening match as the world No.2 cruised to a 6-3 6-1 victory.
It took Halep one hour and 40 minutes to dispatch Mladenovic — who this week added Naomi Osaka's former coach Sascha Bajin to her team — in the first rubber, although Romania's lead was cut when Caroline Garcia overcame Mihaela Buzarnescu 6-3 6-3.
Aiming to propel Romania into its first Fed Cup final, Halep dropped just four games and broke Mladenovic five times at Kindarena.
Mladenovic did well to offer some resistance late in the opening set before breaking Halep's serve at the start of the second, but the 2018 French Open winner swiftly regained control to ease to victory.
Fortunately for two-time champion France, world No.21 Garcia restored parity, winning five break points over the course one hour and 26 minutes against with Buzarnescu, leaving the tie finely balanced.
Garcia and Halep get things started, before Mladenovic takes on Buzarnescu in the final singles rubber.