Serena Williams recovered from losing the first set against qualifier Kaja Juvan.
Williams, a seven-time Wimbledon winner, found her range at the start of the second set with a break.
In front of the watching Duchess of Sussex, she went on to beat the 18-year-old Slovenian 2-6 6-2 6-4.
The end of that game was met with a loud cheer as it was confirmed that Andy Murray's doubles match would be next up on Court One.
Meanwhile, American Lauren Davis produced some Independence Day fireworks as she dumped defending Wimbledon champion Angelique Kerber out in the second round.
Lucky loser Davis fought back from one set behind to claim a stunning 2-6 6-2 6-1 victory over the German on Court Two.
Despite not winning a tournament since beating Serena Williams in the final at SW19 last year, Kerber has shown some good recent form, including reaching the final in Eastbourne last week.
The 31-year-old avoided becoming the first ladies' champion to be defeated in the first round the following year since Steffi Graf in 1994 after beating compatriot Tatjana Maria on Tuesday.
However, Kerber came unstuck second time around against Davis, who responded after losing the first set 6-2.
At that point it looked like Kerber would go on to secure a second consecutive straight-sets win, but Davis did not read the script and won 12 of the next 15 games to seal a place in the third round.
