World number four Sharapova hit nine double faults in the match, but broke twice in the second set, while Pliskova squandered three break points.
Earlier, world number six Petra Kvitova came from a set down to beat Anastasia Pavlyuchenkova 2-6 6-1 6-1.
Kvitova, who helped the Czechs win the 2014 title, faces Sharapova on Sunday before Pliskova meets Pavlyuchenkova.
Should the teams still be level, a doubles rubber will decide the tie.
"I was nervous throughout and made some errors at inappropriate times, but overall I'm really happy," said five-time Grand Slam winner Sharapova.
"I didn't serve my best and that's something that I'll definitely need to improve."
Russia's Maria Sharapova beat Czech Republic's Karolina Pliskova 6-3 6-4 to level the Fed Cup final in Prague.